Give me some words which we can use instead of 'Whereas'?

Depending on the context for your use of "whereas," substitutes could be the following: because, considering, since, though, when, while, although, as, considering that, forasmuch as, insomuch as, since, though. Some of these words and phrases--like "foreasmuch as"--are quite formal, but then so is "whereas." I hope this helps you.