Pronunciation: (bā'sis),[key] —n., —pl.-sesPronunciation: (-sēz).[key] 1. the bottom or base of anything; the part on which something stands or rests.
2. anything upon which something is based; fundamental principle; groundwork.
3. the principal constituent; fundamental ingredient.
4. a basic fact, amount, standard, etc., used in making computations, reaching conclusions, or the like: The nurse is paid on an hourly basis. He was chosen on the basis of his college grades. 5. Math.a set of linearly independent elements of a given vector space having the property that every element of the space can be written as a linear combination of the elements of the set.