The words because and as can be used as transition words that indicate causation, and they are nearly synonymous. Because is the more general purpose word meaning ‘as a result of’, and can be used in almost all circumstances. As means ‘with the reason being that’.

Because the male characters in The Great Gatsby build their selves around their wives or lovers, they are vulnerable.

It was not always beneficial to increase the magnetic energy further, as the stator steel was saturated at about 1.8 T.