吗
Means the sentence is a question
[1]
 
Parts Composed of the characters 口 mouth and 马 horse.
Memory hook Resembles a horse pulling a cart. If a traveler on a horse stops she is probably going to ask you a question 吗.
Grammar Note
The character 吗 appears only at the end of a sentence.
Practice
ChineseliterallyEnglish
女子好吗？woman good (question)Is the woman ok?
子女好吗？children good (question)Are the children ok?
女人好吗？woman good (question)Is the woman ok?
人人好吗？everybody good (question)Is everybody well?
口好吗？mouth good (question)Is the opening ok?
人口好吗？population good (question)Is the population ok?
马好吗？horse good (question)Is the horse well?
人马好吗？troops good (question)Are the troops good?
Dialog
ChineseliterallyEnglish
你好吗？you good (question)How are you? Are you ok?
好goodfine. good. ok.
Next
 
[1] 167 buggy by Pearson Scott Foresman from http://commons.wikimedia.org/wiki/File:Buggy_(PSF).jpg, flipped horizontal, under license: Public domain