18-letter words containing z
- witch hazel family — the plant family Hamamelidaceae, characterized by trees and shrubs having alternate, simple leaves, flowers in clusters or heads, and fruit in the form of a double-beaked woody capsule, and including the sweet gum, witch alder, and witch hazel.
- zermelo set theory — (mathematics) A set theory with the following set of axioms: Extensionality: two sets are equal if and only if they have the same elements. Union: If U is a set, so is the union of all its elements. Pair-set: If a and b are sets, so is {a, b}. Foundation: Every set contains a set disjoint from itself. Comprehension (or Restriction): If P is a formula with one free variable and X a set then {x: x is in X and P(x)}. is a set. Infinity: There exists an infinite set. Power-set: If X is a set, so is its power set. Zermelo set theory avoids Russell's paradox by excluding sets of elements with arbitrary properties - the Comprehension axiom only allows a property to be used to select elements of an existing set.
- zion national park — a park in SW Utah. 148 sq. mi. (383 sq. km).
- zone of saturation — the ground below the water table
- zorrilla (y moral) — Joˈsé (hɔˈsɛ ) ; h^ōseˈ) 1817-93; Sp. poet & playwright