What is tonic in music?

In music, tonic is the first note of a scale or key. It is also known as the key note or the home note, as it is often the note where a piece of music begins and ends. The tonic note and the corresponding tonic chord create a sense of stability and resolution in a piece of music, as they are the foundation on which the rest of the musical structure is built. In Western music, the tonic note is often designated by the letter name "T" or "I" (for the first scale degree or "tonic"), and the tonic chord is typically denoted with a Roman numeral "I". The tonic note and chord can also play an important role in modulating or changing keys within a piece of music.