The Gemara and other sources use different words to say that something is permitted. There are "shari" "muttar" "leis lon boh".
Is there any difference in shades of meaning between these and others please?
As WAF said:
"Shari" is Aramaic for "permitted"; "mutar" is Hebrew. If it was a Mishnaic subject, most likely the word would be "mutar."
"Leis lon boh" means "not a problem." (Or literally, there is nothing for us [prohibited] in it.) I.e. a limitation on a prohibition. Usually the context is something like:
It is prohibited to do X; however that's only in circumstance Y. In circumstance Z, leis lon boh.