Vowel Alternations in English

English has many related words which exhibit vowel alternations. They are common in many nouns and verbs. Here are examples:

foot feet

goose geese

tooth teeth

drive drove driven

see saw

cycle cyclical

grateful gratitude

line linear

long length

nation national

pronounce pronunciation

school scholar

south southern

study student

wide width

The pairs grateful/gratitude and pronounce/pronunciation illustrate a phenomenon known as trisyllabic laxing. The stressed vowel becomes lax in trisyllabic words.

Vowel alternations are common in irregular plurals.  They once had the plural marker -s, but it was lost over time.

In many verbs vowel alternations occur. The verbs drive/drove/driven contain three different stressed vowels.

Forms such as cycle/cyclical long/length are derivational. The pair cycle/cyclical contains a noun and adjective while the pair long/length contains an adjective and noun. The pair school/scholar contains two nouns, but the relationship is derivational because school refers to a place and scholar refers to a person.

The list of words illustrates a few of the vowel alternations that occur in English. Such vowel alternations are common not only in English but in many languages. Vowels are more likely to change than consonants because they involve greater airflow through the oral cavity and do not have fixed points of articulation.