n.
1.the blood group whose red cells carry the A antigen
2.a metric unit of length equal to one ten billionth of a meter (or 0.0001 micron)
3.any of several fat-soluble vitamins essential for normal vision
4.one of the four nucleotides used in building DNA
5.(biochemistry) purine base found in DNA and RNA
6.the basic unit of electric current adopted under the Systeme International d'Unites
7.the 1st letter of the Roman alphabet
Idiom of the Day
track (someone or something) down or track down (someone or something)
to search for someone or something
I have been trying to track down an old Beatles album for many months.
