A theorem is a statement that has been proven to be true through logical reasoning. The crossword solutions for the term 'theorem' include 'principium' (10 letters), which is Latin for 'BEGINNING' or 'FOUNDATION'; 'DOCTRINE' (8 letters), which is a set of beliefs or principles; 'HYPOTHESIS' (10 letters), which is an educated guess or ASSUMPTION; 'POSTULATE' (9 letters), which is a statement accepted as true without proof; 'PRINCIPLE' (9 letters), which is a FUNDAMENTAL truth or LAW; 'PROPOSITION' (11 letters), which is a statement that can be either true or false; 'ASSUMPTION' (10 letters), which is something taken for granted; 'OPINION' (7 letters), which is a personal BELIEF; 'BELIEF' (6 letters), which is a strong feeling of trust in someone or something; 'LAW' (3 letters), which is a RULE of conduct; 'FUNDAMENTAL' (11 letters), which is a basic PRINCIPLE; 'BASIS' (5 letters), which is the FOUNDATION of something; 'FAITH' (5 letters), which is a strong BELIEF in something; 'STANDARD' (8 letters), which is a level of quality or achievement; 'RULE' (4 letters), which is a regulation or guideline; 'AXIOM' (5 letters), which is a self-evident truth; and 'IDEA' (4 letters), which is a thought or concept.