Tiananmen is translated into English as "The Gate of Heavenly Peace". It is pronounced "tyEnn-unn-menn", not "tee-AN-a-men".
The Chinese characters (hànzĭ) are:

tiān, meaning heaven, (amongst other things; "sky", "God" etc.);

ān, meaning peace; and

门 (門)

mén, meaning gate

The characters for "square" are:

广 (廣)

guăng, meaning wide; and

场 (場)

chăng, meaning open space.

Here is the whole word:

天安门广场 (天安門廣場)

The characters in parentheses ( ) indicate the traditional characters, as used in Taiwan, Hong Kong, Japan and Korea, etc. Mainland China uses primarily the simplified characters. Read about the differences at Simplified Chinese vs. Complicated Chinese

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