Englishfor English speakers
a
Determinative
—
A is used when the following word could be any of a certain type.
Compare "A book I saw on the shelf" and "The book I gave you yesterday".
a
Noun
—
A is the first letter of the alphabet.
The letter "a" comes before "b".
—
In some schools, an A is a very high grade.
Ron got an A on his earth science test.
via
Preposition
—
You use via to mean the path that something takes when it goes somewhere (the places it goes through before it gets there).
We can send video, audio and data from any point in the UK, via satellite.
This became part of our route from Liverpool to Manchester via Runcorn.
John sent the message to Yoko via Hamid.