while as

Webster's Dictionary (GCIDE)

1.During the time that; as long as; whilst; at the same time that; as, while I write, you sleep. "While I have time and space." --Chaucer. [1913 Webster]

Use your memory; you will sensibly experience a gradual improvement, while you take care not to overload it.— I. Watts.[1913 Webster]

2.Hence, under which circumstances; in which case; though; whereas. [1913 Webster]

While as, While that, during or at the time that. [Obs.] [1913 Webster]