A Special Assessment District (S.A.D.) is a geographic area in which the market value of real estate is enhanced due to the influence of a public improvement and in which a tax is apportioned to recover the costs of the public improvement.
Void, voidable, and unenforceable contracts: (1) A void contract is one without any legal effect from the beginning. (2) A voidable contract is one that a party may elect to avoid or ratify. (3) An unenforceable contract is one otherwise valid but for which some defense exists extraneous to formation.
See: invalid, void. (of a contract) unable to be enforced by either party or unenforceable by one. In the former case, the contract is for practical purposes void, but in the latter case the other party may enforce. This question arises most often in relation to ILLEGAL CONTRACTs.