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01
un
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
un
used before a noun when we are not talking about a specific person or thing
Esempio
She received a letter from a friend.
She brought a gift for the birthday party.
She received a letter from a friend.
They are going on a trip next week.
He has a problem that needs solving.
02
UN
used to show someone or something belongs to a group or type
01
UN
the musical pitch A, which is a specific note in the diatonic scale commonly used in Western music
What is "A"?
In music, the pitch "A" is a specific note that is used as a reference point for tuning and playing. It is one of the twelve notes in the musical scale and is represented by the letter "A". Each "A" note can be higher or lower in pitch depending on the octave. For example, "A4" is a common reference pitch that vibrates at 440 Hertz and is often used to tune musical instruments. This note helps musicians keep their music in tune and create harmonious sounds.
02
UN
a metric unit of length equal to one ten billionth of a meter (or 0.0001 micron); used to specify wavelengths of electromagnetic radiation
03
UN
the blood group whose red cells carry the A antigen
04
UN
the 1st letter of the Roman alphabet
05
UN
one of the four nucleotides used in building DNA; all four nucleotides have a common phosphate group and a sugar (ribose)
06
UN
(biochemistry) purine base found in DNA and RNA; pairs with thymine in DNA and with uracil in RNA
Esempio
She found a job at a company downtown.
She bought a new book yesterday.
There is a movie theater in the mall.
She found a job at a company downtown.
They were excited to see a shooting star in the sky.
