The Subject Particle 가 and 이
The subject particle is added to a word to indicate that it is the subject of a clause. 가 is added to a noun ending in vowel and 이 is added to a noun ending in a consonant.
If the predicate at the end of the clause is a verb the subject is the executor of the verb.
If the predicate at the end of the clause is an adjective, the adjective describes the subject.