Language (Speech) is divided into certain strata or levels. The linguists distinguish basic and nonbasic (sometimes they term them differently: primary and secondary) levels. This distinction depends on whether a level has its own unit or not. If a level has its own unit then this level is qualified as basic or primary. If a level doesn't have a unit of its own then it is a non-basic or secondary level. Thus the number of levels entirely depends on how many language (or speech) units in language.