they eliminate possible grammatical ambiguities. -a or -ya (Hangul: 아, 야) is a casual title used at the end of names. It is not gender exclusive. If a name ends in a consonant -a is used (e.g. Jinyoung-a 진영아), while -ya is used if the name ends in a vowel (e.g. Yeji-ya 예지야). -a / -ya is used only between close friends and people who are familiar with each other, and its use between strangers or distant acquaintances would be considered extremely rude. -ya / -a is only used hierarchically horizontally or downwards: an adult or parent may use it for young children, and those with equal social standing may use it with each other, but a young individual will not use -a or -ya towards one who is older than oneself or holds a higher status than oneself. Middle Korean had three classes of the vocative case but practically only -아 / -야 is remaining in everyday life. -여 / -이여 is only used in literature and archaic expressions, and -하 has completely disappeared. See Korean vocative case for more information. Ssi Ssi (씨, 氏) is the most commonly used honorific used amongst people of approximately equal speech level. It is attached after the full name, such as 'Lee Seokmin ssi'' (이석민 씨), or simply after the first name, ''Seokmin ssi'' (석민 씨) if the speaker is more familiar with someone. Appending ssi to the surname, for instance ''Park ssi'' (박 씨) can be quite rude, as it indicates the speaker considers himself to be of a higher social status than the person he is speaking to. Nim, -nim Nim (Hangul: 님) (by itself after a proper noun) is the highest form of honorifics and above ssi. Nim will follow addressees' names on letters/emails and postal packages. It is often roughly translated as "Mr." or "Ms./Mrs.". -nim (as an affix) is used as a commonplace honorific for guests, customers, clients, and unfamiliar individuals. -nim is also used towards someone who is revered and admired for having a significant amount of skill, intellect, knowledge, etc. and is used for people who are of a higher rank than oneself. Examples include family members (eomeonim 어머님 & abeonim 아버님), teachers (seonsaengnim 선생님), clergy (e.g. pastors – moksanim 목사님), and gods (haneunim 하느님 / hananim 하나님). Seonbae/hubae Seonbae (선배, 先輩) is used to address senior colleagues or mentor figures relating to oneself (e.g.