I think you might mean at the beginning of a word, not a sentence. The only affix that can come at the beginning of a word is called a prefix.
Examples of prefixes:
pre-
re-
bio-
auto-
A prefix is added to the beginning of a word and a suffix is added to the end of one. Example: prefix:dis- suffix:-ing
An affix is a bound morpheme that is attached to a base word to create a new word, while a suffix is a specific type of affix that is attached to the end of a base word. Suffixes typically change the grammatical function or meaning of the base word.
An affix is a morpheme attached to a root word to create a new word or change its meaning or function. For example, the prefix "un-" added to the word "happy" changes its meaning to "unhappy."
Infixes are morphemes that are attached within a word to change its meaning or grammatical category. They are different from prefixes (attached at the beginning) and suffixes (attached at the end) because they are inserted into the middle of a word. Ancient languages like Latin and Greek often use infixes.
A prefix, such as "pre" added to "view" to create "preview".
Suffix is attached in the end. Eg: word "able" which can be added to avoidable, comfortable, etc. Prefix is attached in the beginning. Eg: Dr. for Doctor, ER. for Engineer.
There is another way to describe an affix attached to the beginning of a word. It is typically known as a morpheme.
suffix
A word element attached to a root word that changes its meaning is called an "affix."
Affix, a grammatical element that is combined with a word, stem, or phrase to produce derived and inflected forms. There are three types of affixes: prefixes, unfixes, and suffixes.
which not fixed term....... Affix is a verb it means to attach, stick, join. john affixed a stamp to the letter.
A suffix is attached to the end of a word. A prefix is attached to the beginning of a word.
An affix is a word added to a word to form a new word. For example, 'trans-' is a prefix (type of affix) meaning 'move', or 'change'. An example of a word beginning with 'trans-' is transform, which means to change in shape.
An afformative is another name for an affix - a short portion of a word attached to a stem to form a new word.
I think that the tha antonym of affix is to unfasten, but I am not completely sure....
A prefix, such as "pre" added to "view" to create "preview".
feat is the base word and no affix
A prefix is a type of affix attached to a stem which modifies the meaning of that stem.