AA: Duplicated characters (AA) are written together:
tiāntiān 天天，every day
xiǎoxiǎo 小小，little
màn màn 慢慢，slowly
mǎnmǎn 满满, to the brim, fully
hǎohǎo 好好, in a proper way
ABAB: two characters duplicated (ABAB) are written separated:
cānkǎo cānkǎo 参考参考 - as a reference
tǎolùntǎolùn 讨论讨论 - discuss
jiěshì jiěshì 解释解释 - explain
AABB: a hypen is written with the schema
lǎolǎo－shishi 老老实实 （ honestly; conscientiously; in earnest）
kāikāi－xīnxīn 开开心心 （happily)
jiājiā－hùhù 家家户户 （each and every family; every household)
