1.  ca(n = noun.substance) atomic number 20, calcium - a white metallic element that burns with a brilliant light; the fifth most abundant element in the earth's crust; an important component of most plants and animals;
is a kind of metal, metallic element
has particulars: calcium ion, factor iv

2.  ca(n = noun.location) calif., california, golden state - a state in the western United States on the Pacific; the 3rd largest state; known for earthquakes;
is a kind of american state
is a part of southwest, southwestern united states, america, the states, u.s., u.s.a., united states, united states of america, us, usa
has parts: channel islands national park, kings canyon national park, lassen volcanic national park, redwood national park, sequoia national park, yosemite national park, anaheim, bakersfield, barstow, berkeley, beverly hills, chula vista, eureka, fresno, long beach, city of the angels, los angeles, monterey, oakland, palo alto, pasadena, redding, riverside, capital of california, sacramento, san bernardino, san diego, san francisco, san jose, san mateo, san pablo, santa ana, santa barbara, santa clara, santa cruz, big sur, silicon valley, colorado desert, death valley, mohave, mohave desert, mojave, mojave desert, lake tahoe, donner pass, golden gate, klamath, klamath river, monterey bay, russian river, sacramento river, salton sea, san andreas fault, san fernando valley, san joaquin river, san joaquin valley, mount shasta, shasta, high sierra, sierra nevada, sierra nevada mountains

   the chemical symbol for calcium, the fifth most abundant element in the earth's crust. [WordNet 1.5]

ca, abbr.
1 US California (in official postal use).
2 Sc. & Can. chartered accountant.

ca, symb. Chem. the element calcium.