noun

• A physical base or foundation.
• A starting point, base or foundation for an argument or hypothesis.
• An underlying condition or circumstance.
• A regular frequency.
• (agriculture, trading) The difference between the cash price a dealer pays to a farmer for his produce and an agreed reference price, which is usually the futures price at which the given crop is trading at a commodity exchange.
• (linear algebra) In a vector space, a linearly independent set of vectors spanning the whole vector space.
• (accounting) Amount paid for an investment, including commissions and other expenses.
• (topology) A collection of subsets ("basis elements") of a set, such that this collection covers the set, and for any two basis elements which both contain an element of the set, there is a third basis element contained in the intersection of the first two, which also contains that element.