As a Germanic language, the English language has many irregular verbs, overwhelmingly of Germanic origin, except for some words such as catch, approaching 200 in normal use – and significantly more if prefixed forms are counted. In most cases, the irregularity concerns the past tense (also called preterite) or the past participle. The other inflected parts of the verb – the third person singular present indicative in -[e]s, and the present participle and gerund form in -ing – are formed regularly in most cases. There are a few exceptions: the verb be has irregular forms throughout the present tense; the verbs have, do, and say have irregular -[e]s forms; and certain defective verbs (such as the modal auxiliaries) lack most inflection.
Irregular verbs in Modern English include many of the most common verbs: the dozen most frequently used English verbs are all irregular. New verbs (including loans from other languages, and nouns employed as verbs) usually follow the regular inflection, unless they are compound formations from an existing irregular verb (such as housesit, from sit).
Irregular verbs typically followed more regular patterns at a previous stage in the history of English. In particular, many such verbs derive from Germanic strong verbs, which make many of their inflected forms through vowel gradation, as can be observed in Modern English patterns such as sing–sang–sung. The regular verbs, on the other hand, with their preterites and past participles ending in -ed, follow the weak conjugation, which originally involved adding a dental consonant (-t or -d). Nonetheless, there are also many irregular verbs that follow or partially follow the weak conjugation.
For information on the conjugation of regular verbs in English, as well as other points concerning verb usage, see English verbs.
Development Most English irregular verbs are native, derived from verbs that existed in Old English. Nearly all verbs that have been borrowed into the language at a later stage have defaulted to the regular conjugation. There are a few exceptions, however, such as the verb catch (derived from Old Northern French cachier), whose irregular forms originated by way of analogy with native verbs such as teach.
Most irregular verbs exist as remnants of historical conjugation systems. When some grammatical rule became changed or disused, some verbs kept to the old pattern. For example, before the Great Vowel Shift, the verb keep (then pronounced /keːp/, slightly like "cap", or "cape" without the glide) belonged to a group of verbs whose vowel was shortened in the past tense; this pattern is preserved in the modern past tense kept (similarly crept, wept, leapt, left). Verbs such as peep, which have similar form but arose after the Vowel Shift, take the regular -ed ending.
The force of analogy tends to reduce the number of irregular verbs over time, as irregular verbs switch to regular conjugation patterns (for instance, the verb chide once had the irregular past tense chid, but this has given way to the regular formation chided). This is more likely to occur with less common verbs (where the irregular forms are less familiar); hence it is often the more common verbs (such as be, have, take) that tend to remain irregular. Many irregular verbs today have coexisting irregular and regular forms (as with spelt and spelled, dreamt and dreamed, etc.).
In a few cases, however, analogy has operated in the other direction (a verb's irregular forms arose by analogy with existing irregular verbs). This is the case with the example of catch given above; others include wear and string, which were originally weak verbs, but came to be conjugated like the similar-sounding strong verbs bear and swing.
In American English, the regular forms of verbs account for more than 90% of instances, whereas British English has a regular form frequency of 69% according to a 1991 study.
The verb forms described in this article are chiefly those that are accepted in standard English; many regional dialects have different irregular forms, such as sneak–snuck and dive-dove, common in the United States, as opposed to standard sneaked and dived respectively. In particular, it is fairly common in some types of non-standard speech to use (standard) past tenses as past participles, and vice versa; e.g. "have went" instead of "have gone" in Southern American English.
Groups The irregular verbs of Modern English form several groups with similar conjugation pattern and historical origin. These can be broadly grouped into two classes – the Germanic weak and strong groups – although historically some verbs have moved between these groups. There are also a few anomalous cases: the verbs be and go, which demonstrate suppletion; the verb do; and the defective modal verbs.
Strong verbs Many irregular verbs derive from Germanic strong verbs, which display the vowel shift called ablaut, and do not add an ending such as -ed or -t for the past forms. These sometimes retain past participles with the ending -[e]n, as in give–gave–given and ride–rode–ridden, but in other cases this ending has been dropped, as in come–came–come and sing–sang–sung. This verb group was inherited from the parent Proto-Germanic language, and before that from the Proto-Indo-European language. It was originally a system of regular verbs, and in Old English and modern German the system remains more or less regular; however in Modern English relatively few verbs continue to follow such a pattern, and they are classed as irregular.
Verbs that retain a strong-type inflection in modern English and add -[e]n in the past participle include bear, beat, beget, bite, blow, break, choose, cleave, draw, drive, eat, fall, fly, forbid, forget, forsake, freeze, get (but with past participle got in British English), give, grow, know, lie, ride, rise, see, shake, shear, slay, smite, speak, steal, stride, strive, swear, take, tear, throw, tread, wake, weave, and write.
Those that do not add -[e]n in the usual past participle include become, begin, bind, burst, cling, come, drink, fight, find, fling, grind, hang, hold, let, ring, run, seek, shed, shine, shit, shoot, shrink, sing, sink, sit, slide, sling, slink, slit, spin, spring, stand, sting, stink, strike, swim, swing, win, wind and wring.
The verbs sow and swell are now usually regular in the past tense, but retain the strong-type past participles sown and swollen. Other verbs retain participles in -n for certain adjectival uses and distinguish them from other usage in perfect tenses ("He is drunk" vs "drunken sailor", "The shirt has shrunk" vs "shrunken hands" or "The ship was sunk" vs "sunken cheeks"). The participle in -n may sometimes be limited to certain specific usage, as in molten used only to refer to metals (compare "molten steel" vs "melted butter"). Sometimes the connection between the infinitive and the adjective (i.e. originally the past participle form) is not perceived as obvious any more, e.g. seethe – sodden. The verb crow is now regular in the past participle, but the strong past tense crew is sometimes used.
Some originally weak verbs have taken on strong-type forms by analogy with strong verbs. These include dig, dive (when dove is used as the past tense), hide, prove (when proven is used as the past participle), saw (past participle sawn), sew (past participle sewn), show (past participle shown), spit, stick, strew, string, and wear (analogy with bear).
For indication of the groups of strong verbs the listed words belong to, see the table at List of English irregular verbs.
Weak verbs Some other irregular verbs derive from Germanic weak verbs, forming past tenses and participles with a -d or -t ending (or from originally strong verbs that have switched to the weak pattern). The weak conjugation is also the origin of the regular verbs ending in -ed; however various historical sound changes (and sometimes spelling changes) have led to certain types of irregularity in some verbs. The main processes are as follows (some verbs have been subject to more than one of these).These processes are described in Oxford English Dictionary, Second Edition, entry for "-ed". Some weak verbs with long vowels in their present tense stems (such as keep) took a short vowel in the past tense and past participle (kept).The conditions under which this and other instances of long and short vowel alternation arose in English are not fully understood. See for example Minkova D., Stockwell R.P., The origins of long-short allomorphy in English, in: Advances in English Historical Linguistics, Fisiak, Krygier (eds.), de Gruyter, 1998. In some weak verbs ending in a final -t or -d, this final consonant coalesced (contracted) with the weak past ending to leave a single -t or -d in the past forms. Some verbs ending in l or n had their past ending irregularly devoiced to -t, and in a few verbs ending with a v or z sound (leave, lose), both that sound and the past ending were devoiced. (The regular ending -ed is also devoiced after voiceless consonants in regular verbs, as described under , but this is not now shown in the spelling – for example, the -ed in blessed and whipped is pronounced as a t, and these words were formerly written blest and whipt. The spelling -t following a voiceless consonant is retained for verbs that display an irregularity, as in kept and cost.) Some weak verbs continue the vowel shift called Rückumlaut ("reverse umlaut"). Details of the history of these verbs can be found under Germanic weak verb; those with -gh- in the spelling were also affected by the Germanic spirant law. A few weak verbs have undergone additional contractions or vowel shortenings in their past or present tense forms. A few verbs are regular in their spoken forms, but have irregular spelling.
The irregular weak verbs (being in normal use) can consequently be grouped as follows: Verbs with vowel shortening: creep, flee, hear, keep, leap, shoe (when shod is used), sleep, sweep and weep. (Of these, creep, flee, leap, sleep and weep derive from verbs that were originally strong.) Verbs with vowel shortening and devoicing of the ending: deal, dream, feel, kneel, lean, leave, lose (originally strong) and mean. Some of the verbs in this and in the preceding group have alternative regular forms, such as dreamed and leaped. Verbs with coalescence of consonants: bet, bid, cast, cost, cut, fit, hit, hurt, knit, put, quit, rid, set, shed, shut, split, spread, thrust, wed and wet. Some of these verbs have alternative regular forms, such as wedded and wetted. (The verb hoist behaves similarly to verbs in this group, but this was originally itself a past form of the now obsolete verb hoise; similarly clad was originally – and sometimes still is – a past form of clothe.) Verbs with coalescence of consonants and devoicing of the ending: bend, build, lend, rend, send, spend. Verbs with coalescence of consonants and vowel shortening: bleed, breed, feed, lead, light, meet, read (past tense and past participle also spelt read, but pronounced with a short vowel /ɹɛd/), and speed. Verbs with devoicing of the ending and no other irregularity: burn, dwell, learn, smell, spell, spill and spoil. Most of these have regular -ed forms as alternatives. Verbs continuing the Rückumlaut pattern: bring–brought, buy–bought, seek–sought, sell–sold, teach–taught, tell–told, and think–thought. The borrowed verb catch (caught) has also fallen into this pattern as a result of analogy. Verbs with additional contractions and shortenings: have–has–had, make–made, say–says–said (where says and said are pronounced with a short vowel ). (The verb do has a similar vowel shortening in does and done; see below.) Verbs irregular only in spelling: lay–laid, pay–paid (although in the meaning "let out", of a rope etc., pay may have the regular spelling payed).