What is the term for a musical composition for a solo instrument?

The word 'sonata' itself comes from the Italian 'sonare', meaning 'sound'. In relation to classical music, sonata means the piece is performed by a solo instrument, typically a piano or another instrument accompanied by a piano – rather than being something that is performed vocally (the term 'cantata' is used to describe a piece that is sung). Among the most well-known sonatas is Beethoven's Piano Sonata No. 14 in C-sharp Minor, which is also known as the Moonlight Sonata.

Source: BBC Music Magazine