Greek, unlike English, is a highly inflected language. Inflection refers to the changes that words undergo in accordance with their grammatical function in a sentence. Verbs in Greek consist of two basic parts: a stem, which contains the dictionary meaning of the word, and one or more affixes, which indicate the function of the word in the particular sentence where it occurs. An affix added to the beginning of a word is called a prefix, one that is added within a word is called an infix, and one that is added to the end of a word is called a suffix. English verbs such as “break” are illustrative: “break-” is the present stem, and by adding the third person singular suffix, we get “breaks.” “Brok-” is the past stem, and “broken” is the part participle.
Notice, however, the forms for the English verb “have” and their German and Spanish equivalents (see chart).