a

/ˈeɪ/

/ˈeɪ/, /ə/

used when we want to talk about a person or thing for the first time or when other people may not know who or what they are

1.1

used before a noun when we are not talking about a specific person or thing

used to show someone or something belongs to a group or type

the musical pitch A, which is a specific note in the diatonic scale commonly used in Western music

a metric unit of length equal to one ten billionth of a meter (or 0.0001 micron); used to specify wavelengths of electromagnetic radiation

synonyms : angstrom

the blood group whose red cells carry the A antigen

synonyms : group A

the 1st letter of the Roman alphabet

synonyms : a

the basic unit of electric current adopted under the Systeme International d'Unites

synonyms : amp

any of several fat-soluble vitamins essential for normal vision; prevents night blindness or inflammation or dryness of the eyes

one of the four nucleotides used in building DNA; all four nucleotides have a common phosphate group and a sugar (ribose)

(biochemistry) purine base found in DNA and RNA; pairs with thymine in DNA and with uracil in RNA

synonyms : adenine

Examples

1. The wheel of the bicycle had a hub at its center.

2. Opportunity makes a thief.

3. A pilot must have good vision and quick reflexes.

4. My grandmother made a dress for me.