2. 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.

2.1 Strong verbs

A large number of the 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, 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, get (but with past participle gotten in American English), grind, hang, hold, let, ring, run, shed, shine, shit, shoot, shrink, sing, sink, sit, slide, sling, slink, slit, spin, spring, stand, sting, stink, strike, swim, swing, win, wind and wring.

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, mow, 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.

2.2 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 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).

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).

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 English verbs: Past tense, 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), 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 /ɛ/). (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).

For weak verbs that have adopted strong-type past tense or past participle forms, see the section above on strong verbs.