Spoken and manga Japanese is full of contractions/abbreviations. Some of them are widely known and used while others are not. It can make things rather difficult for a non-native speaker. Here's a short list of some of the random ones that I often use/hear or have simply stuck in my head:
konbini コンビニ = convenience store コンビニエンスストア
(Ubiquitous in Japan and actually very very convenient)
shaapen シャーペン = sharp pencil シャープペンシル
mechanical pencil
K.Y. = kuuki yomenai 空気読めない
can't read the atmosphere, clueless
goukon 合コン= goudou kompa 合同コンパ
group blind date (a group of guys meets with a group of girls in equal numbers)
konkatsu 婚活= kekkon katsudou 結婚活動
marriage hunting; activities leading to marriage (e.g. dating, courtship, etc.)
enren 遠恋 = enkyori renai 遠距離恋愛
long distance relationship
enkou 援交 = enjo kousai 援助交際
dating with compensation; schoolgirl prostitution
(Got this from the Kimi ni Todoke 君に届け manga. My Japanese teacher friend was more than a little surprised when I asked her what it meant.)
konmisu コンミス = concert mistress コンサートミストレス
apparently the concert master/mistress is second only to the conductor in an orchestra
paarii パーリー = part leader パートリーダー
eg. the trumpets' (part) leader
(Got this from the Aozora Yell: Yell for the Blue Sky 青空エール manga, whose main character is part of the school brass band. I think the short form sounds an awful lot like the French/Japanese pronunciation of "Paris"...)
*TKG = tamago kake gohan 卵かけご飯
a dish of rice (gohan) topped with (raw) egg (tamago), usually mixed with a little soy sauce
(*some boys in one of my junior high school made this one up)
*daijoubanai = daijoubu de wa nai 大丈夫ではない
not OK
(*another one made up by some of my junior high school boys)
Fellow students of Japanese, what are some of your "favourites"?
(Incidentally, mine are TKG and daijoubanai