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basal adjective (technical) forming or belonging to a bottom layer or base: basal cells of the skin

basic (to sth): forming the part of sth that is most necessary and from which other things develop: basic information / facts / ideas the basic principles of law Drums are basic to African music. 2- of the simplest kind or at the simplest level: The campsite provided only basic facilities. My knowledge of French is pretty basic. 3- [only before noun] necessary and important to all people: basic human rights the cost of basic foods 4- before anything extra is added: The basic pay of the average worker has risen by 3 per cent.

Basic means something necessary, simple or fundamental. Basal is something that relates or connect to a base or any point of origin.

Basic refers to: 1.Pertaining to or constituting a base or basis "a basic fact"; "the basic ingredients"; "basic changes in public opinion occur because of changes in priorities" 2.Reduced to the simplest and most significant form possible without loss of generality "a basic story line" 3.Serving as a base or starting point a basic course in Russian"; "basic training for raw recruits"; "a set of basic tools" While Basal 1.Especially of leaves; located at the base of a plant or stem; especially arising directly from the root or rootstock or a root-like stem "basal placentation" 2.Serving as or forming a base 3.Of primary importance cowboy...