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A typical English verb has five principal parts:
In English, only strong verbs like write may have all five distinct parts; in weak verbs, the preterite and past participle are identical, e.g. bake, bakes, baking, baked, baked. The highly irregular verb to be has eleven forms: be, am, art, is, are, being, was, wast, were, been, wert, although art, wast, and wert, forms used with thou, are archaic and obsolete.
Most of the strong verbs that survive in modern English are considered to be "irregular verbs". Irregular verbs in English come from several historical sources; some are technically strong verbs (i.e. their forms display specific vowel changes of the type known as ablaut in linguistics); others have had various phonetic changes or contractions added to them over the history of English.
The uses of the principal parts of the English forms are:
The infinitive in English is the naked root form of the word. When it is being used as a verbal noun, the particle to is usually prefixed to it. When the infinitive stands as the predicate of an auxiliary verb, to may be omitted, depending on the requirements of the idiom.
The third person singular in regular verbs in English is distinguished by the suffix -s. In English spelling, this -s is added to the stem of the infinitive form: run > runs. In Early Modern English, some dialects distinguished the third person singular with the suffix -th; after consonants this was written -eth, and some consonants were doubled when this was added: run > runneth
If the base ends in a sibilant sound like /s/, /z/, /S/, /tS/ (see SAMPA) that is not preceded by a British English, as an exception, the final "l" is subject to the doubling rule: yodel > yodelling (American English yodeling).
If the final consonant of a word subject to the doubling rule is -c, that consonant is doubled as -ck: panic > panicking
Irregular forms include:
In weak verbs, the preterite is formed with the suffix -ed: work > worked
If the base ends in e, -d is simply added to it: hone > honed; dye > dyed
Where the base ends in a consonant plus y, the y changes to i before the -ed is added; deny > denied
Where the base ends in a vowel plus y, the y is retained: alloy > alloyed
The rule for doubling the final consonant in regular weak verbs for the preterite is the same as the rule for doubling in the present participle; see above.
Many strong verbs and other irregular verbs form the preterite differently, for which see that article.
In regular weak verbs, the past participle is always the same as the preterite.
Irregular verbs may have separate preterites and past participles; see the article on English irregular verbs.
English verbs, like those in many other western European languages, have more tenses than forms; tenses beyond the ones possible with the five forms listed above are formed with auxiliary verbs, as are the passive voice forms of these verbs. Important auxiliary verbs in English include will, used to form the future tense, shall, formerly used for the future tense, but now used mostly for commands and directives; be, have, and do, which are used to form the supplementary tenses of the English verb, to add aspect to the actions they describe, or for negation.
English verbs display complex forms of negation. While simple negation was used well into the period of early Modern English (Touch not the royal person!) in contemporary English negation almost always requires that the negative particle be attached to an auxiliary verb such as do or be. *I go not is archaic; I don't go or I am not going are what contemporary idiom requires.
English exhibits similar idiomatic complexity with the