助詞N5
〜は
topic marker / contrast
Structure
N + は + 〜
Explanation
Marks the topic or contrast of a sentence. N+は = as for N. Contrast with が: は is known/old topic, が is new info subject. Read as わ.
Examples
私は田中です。
I am Tanaka.
昨日は雨でしたが、今日は晴れです。
It rained yesterday, but today is sunny.
Note
は=topic (scope of sentence), が=subject (doer). Big topic=は, small subject=が: 象は鼻が長い (As for elephants, their noses are long).