the verb. This is the case with certain strong verbs, where historical sound changes have led to a leveling of the vowel modifications: for example, let has both past tense and past participle identical to the infinitive, while come has the past participle identical (but a different past tense, came). The same is true of the verbs listed above under as having undergone coalescence of final consonants (and without other irregularities such as vowel shortening or devoicing of the ending): bet, bid, etc. (these verbs have infinitive, past tense and past participle all identical, although some of them also have alternative regular forms in -ed). The verb read has the same spelling in all three forms, but not the same pronunciation for the past tense and past participle , as it exhibits vowel shortening. In a few cases the past tense of an irregular verb has the same form as the infinitive of a different verb. For example, bore and found may be past tenses of bear and find, but may also represent independent (regular) verbs of different meaning. Another example is lay, which may be the past tense of lie, but is also an independent verb (regular in pronunciation, but with irregular spelling: lay–laid–laid). In fact the past tense verb lay derives from a causative of the verb from which lie derives. The two verbs are sometimes confused, with lay used in the intransitive senses prescriptively reserved for lie. Prefixed verbs Nearly all of the basic irregular verbs are single-syllable words. Their irregular inflected forms are generally single-syllable also, except for the past participles in -en like chosen and risen. However, many additional irregular verbs are formed by adding prefixes to the basic ones: understand from stand, become from come, mistake from take, and so on. As a general rule, prefixed verbs are conjugated identically to the corresponding basic verbs; e.g understand–understood–understood and become–became–become, following the patterns of stand–stood–stood and come–came–come. However, there are occasional differences: in British English, for instance, the past participle of get is got, (as opposed to gotten as in North American English) while that of forget is forgotten. Only a few irregular verbs of more than one syllable cannot be analyzed as prefixed compounds of monosyllables. There is begin–began–begun (this is from Old English bēgun "to be getting or be finding a way", making it equivalent to be- + gate, but it has moved