There are a few words that can be used as synonyms for “while” when used as a noun meaning “a short period of time,” including:
Duration
Time
Period
The following words can be used as synonyms for “while” when it is used as a subordinating conjunction that indicates a contrast between two people or things:
Whereas
Although
Though
The QuillBot Paraphrasing Tool can help you vary your vocabulary to express your intended meaning.