“Correct” means “正确的”（zhèng què de）,and “right” also has this meaning. About the two sentences: 1.This shirt is the correct size for you.Translation of this sentence is “这件衣服的尺寸很适合你”.(zhè jiàn yī fú de chǐ cùn hěn shì hé nǐ) 2.That is the right pen you are using.Meaning of this sentence is "这就是适合你用的那支笔".(zhè jiù shì shì hé nǐ de nà zhī bǐ) This sentence translation is literal translation,because I know the meaning of this sentence, but I don't know how to express it .I'm so sorry.