yi- this prefix is used with the words "gesdi" or "tla" to negate a verb. When used alone it expresses the conditional "if", "can", or "could". yaditasga - if he drinks...
g - "I", this is an "A" Class bound pronoun, used before a vowel.
-aditasg- - present verb stem for "drink"
-o'i - habitual tense suffix. In conversation the "i" is often dropped, thus "kawi gaditasgo" I drink coffee.