English Irregular Verbs
Morphological Classification
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Regular and Irregular Verbs

Regular verbs are verbs which take a '-d' or '-ed' suffix in the past and past participle, as in play, played, played and do not change in any other way. All other verbs are irregular.

Strong and Weak Verbs

Weak verbs are all verbs, including the regular verbs, which take a '-d' or '-ed' suffix in the past and past participle. Most weak verbs are regular. They are considered irregular when
a) the regular '-d / -ed' ending is contracted, as in send, sent, sent (not 'sended') or
b) the vowel in the past and past participle is different from the vowel in the infinitive, as in sell, sold, sold or
c) both of these changes occur, as in bring, brought, brought.
Strong verbs do not take a '-d / -ed' suffix. Instead, the vowel in the past and past participle differs from the vowel in the infinitive, as in take, took, taken. The past participle often ends in -n or -en. These verbs have mostly survived from conjugation systems which no longer exist. All strong verbs are irregular.

Classification of Irregular Verbs

Traditional classifications of irregular verbs tend to leave us each time with a mixed bag of morphologically heterogeneous verbs which, in some cases, have long since lost the features that justified their inclusion in a particular group. Any practical classification will therefore be based primarily on morphological considerations which are, however, still determined in a general way by grammar and / or etymology. Six basic groups (three mostly weak, three mostly strong) may be identified.

Weak Classes

Class 1

For the most part, weak verbs which undergo contraction and / or vowel shortening.
1.1 Regular verbs like cut, cut, cut, which keep the same form in infinitive, past and past participle (owing to contraction of the '-ed' ending).
1.2 Verbs like sit, sat, sat, which keep the same form except that the (short) vowel in past and past participle differs from the (short) vowel in infinitive.
1.3 Verbs like meet, met, met, which keep the same form except that the long vowel in infinitive is shortened in past and past participle.
1.4 Verbs like lose, lost, lost, where the long vowel in infinitive is shortened in past and past participle, and which add a contracted regular ending ('-t').
1.5 Verbs like send, sent, sent, which keep the same form except that the infinitive '-d' ending changes to '-t' in past and past participle.
1.6 Verbs like make, made, made, where the infinitive ending changes to '-d' in past and past participle.
 

Class 2

Regular verbs with (alternative) irregular forms.
2.1 Verbs like burn, burnt or burned, burnt or burned, which can add either irregular '-t' or regular '-ed' endings in past and participle but otherwise keep the same form.
2.2 Verbs like pay, paid, paid, which are irregular only in spelling.
 

Class 3

For the most part, weak verbs which look like strong verbs (because of the change to a long vowel in past and past participle).
3.1 Verbs like find, found, found which keep the same form except that the short vowel in infinitive is lengthened in past and past participle.
3.2 Mostly weak verbs like think, thought, thought, where the short vowel in infinitive changes to ' -au' or ' -ou' and which take a ' -t' ending in past and past participle.
3.3 Verbs like tell, told, told, which have vowel change and a regular '-d ending' in past and past participle.
 

Strong Classes

Class 4

For the most part, strong verbs following variants of the 'i - a - u' pattern.
4.1 Verbs which follow the pattern of vowel modification seen in sing, sang, sung.
4.2 Verbs which follow the pattern of vowel modification seen in swing, swung, swung.
 

Class 5

For the most part, strong verbs which take the '-en' ending in the past participle.
5.1 Verbs like bite, bit, bitten, which have infinitive ending in '-t' or 'd' and participle in '-dden' or -'tten'.
5.2 Weak verbs like melt, melted , melted or molten, which have an alternative irregular participle ending in '-en'.
5.3 Strong verbs like give, gave , given which (mostly) show vowel change and participle in '-en'.
 

Class 6

For the most part, strong verbs where the -en ending has contracted to -n.
6.1 Verbs which follow the pattern of vowel modification of blow, blew, blown in past and past participle.
6.2 Verbs like sew, sewed, sewed or sewn, which have an alternative irregular participle ending in '-n'.
6.3 Verbs which follow the pattern of vowel modification of wear, wore, worn.
6.4 Other verbs like see, saw, seen with past participle ending in '-n'.
 

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