The word you are looking for is "polish." To bring something to a finish or to enhance its quality often involves refining or perfecting it, which is encapsulated in the term "polish."
to bring to an end;finish;terminate
A syllable or a word joined to the beginning of a word is called a prefix.
A prefix is added at the beginning of a word.
A prefix is the word element at the beginning of a word.
complete, end, terminate, conclude, finish, finish up, finish off, do, perform, execute, fulfill, consummate, perfect, cap, carry off, carry out, carry through, turn out, bring about, bring off, make happen, settle, effect, bring to an end, bring to a conclusion,
This is called a prefix.
to bring or come to an end synonyms: conclude, finish
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-
It is called a frontispiece.
prefix
A speech at the beginning of a play is called a prologue.
end, stop, finish, ccomplete,ect....... Note: a antonym is the opposite of a word. EX: day:night or happy:sad