if input is available before it starts.
Value is t if waited the full time with no input arriving.
+Redisplay will occur even when input is available if you bind
+`redisplay-dont-pause' to a non-nil value.
+
An obsolete but still supported form is
\(sit-for SECONDS &optional MILLISECONDS NODISP)
Where the optional arg MILLISECONDS specifies an additional wait period,