모여라 << 모이(다) + 어라 모이다 : to gather, flock 어라 : imperative suffix of Haera-che(해라체) 모여라 means "gather here!" https://en.wikipedia.org/wiki/Korean_speech_levels#Haera-che From http://morninglands.com/speech-level-%ED%95%B4%EB%9D%BC%EC%B2%B4-plain-style/ 해라체 Imperative (-어라/아라/해라) There is, however, one special conjugation that is part of 해라체. In fact, this special conjugation is what gives the plain style its Korean name. The special conjugation is for an imperative, like the common -세요 and 지 마세요. The plain style imperative has three potential verb endings: -아라, -어라 or 해라. As you may notice, these verb endings adhere to the general 아/어 conjugation rule. The rules to conjugate any verb in the plain style imperative go as follows: If a verb stem contains either ㅏ or ㅗ, the verb ending you use is -아라. If the verb stem contains neither ㅏ or ㅗ, the verb ending is -어라. All 하다 verbs’s verb ending is 해라.