| a | | |
| n. (quantity) | 1. a, angstrom, angstrom unit | a metric unit of length equal to one ten billionth of a meter (or 0.0001 micron); used to specify wavelengths of electromagnetic radiation. |
| ~ metric linear unit | a linear unit of distance in metric terms. |
| ~ micromicron, picometer, picometre | a metric unit of length equal to one trillionth of a meter. |
| ~ micromillimeter, micromillimetre, millimicron, nanometer, nanometre, nm | a metric unit of length equal to one billionth of a meter. |
| n. (substance) | 2. a, antiophthalmic factor, axerophthol, vitamin a | any of several fat-soluble vitamins essential for normal vision; prevents night blindness or inflammation or dryness of the eyes. |
| ~ fat-soluble vitamin | any vitamin that is soluble in fats. |
| ~ retinol, vitamin a1 | an unsaturated alcohol that occurs in marine fish-liver oils and is synthesized biologically from carotene. |
| ~ dehydroretinol, vitamin a2 | a viscous alcohol that is less active in mammals than is vitamin A1. |
| n. (substance) | 3. a, deoxyadenosine monophosphate | one of the four nucleotides used in building DNA; all four nucleotides have a common phosphate group and a sugar (ribose). |
| ~ nucleotide, base | a phosphoric ester of a nucleoside; the basic structural unit of nucleic acids (DNA or RNA). |
| n. (substance) | 4. a, adenine | (biochemistry) purine base found in DNA and RNA; pairs with thymine in DNA and with uracil in RNA. |
| ~ biochemistry | the organic chemistry of compounds and processes occurring in organisms; the effort to understand biology within the context of chemistry. |
| ~ purine | any of several bases that are derivatives of purine. |
| ~ deoxyribonucleic acid, desoxyribonucleic acid, dna | (biochemistry) a long linear polymer found in the nucleus of a cell and formed from nucleotides and shaped like a double helix; associated with the transmission of genetic information.; "DNA is the king of molecules" |
| ~ ribonucleic acid, rna | (biochemistry) a long linear polymer of nucleotides found in the nucleus but mainly in the cytoplasm of a cell where it is associated with microsomes; it transmits genetic information from DNA to the cytoplasm and controls certain chemical processes in the cell.; "ribonucleic acid is the genetic material of some viruses" |
| n. (quantity) | 5. a, amp, ampere | the basic unit of electric current adopted under the Systeme International d'Unites.; "a typical household circuit carries 15 to 50 amps" |
| ~ current unit | a measure of the amount of electric charge flowing past a circuit point at a specific time. |
| ~ milliampere, ma | one thousandth of an ampere. |
| ~ abamp, abampere | a unit of current equal to 10 amperes. |
| n. (communication) | 6. a | the 1st letter of the Roman alphabet. |
| ~ latin alphabet, roman alphabet | the alphabet evolved by the ancient Romans which serves for writing most of the languages of western Europe. |
| ~ alphabetic character, letter of the alphabet, letter | the conventional characters of the alphabet used to represent speech.; "his grandmother taught him his letters" |
| n. (body) | 7. a, group a, type a | the blood group whose red cells carry the A antigen. |
| ~ blood group, blood type | human blood cells (usually just the red blood cells) that have the same antigens. |
| an | | |
| n. (communication) | 1. an, associate in nursing | an associate degree in nursing. |
| ~ associate degree, associate | a degree granted by a two-year college on successful completion of the undergraduates course of studies. |
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