why does わ become は in certain sentences

こんにち　は :) This would be the perfect example of what I mean. Why is this written Konnichi ha instead of konnichi wa in kana? Logically it would be こんにちわ wouldn't it?

Adam-san konnichiwa! ----Hiragana は and わ ---- The sound *'wa'* is always written with the Hiragana わ such as in わかり ます (wakarimasu) for "I understand". However there is one EXCEPTION to this rule. The topic marker! When *'wa'* is the topic marker - it is written は. When は appears somewhere else, it is read *'ha'*, as in はい (hai) for "yes" - BUT as a topic marker, it is always read as *'wa*'. It is a bit tricky when you want to write the sound *'wa'* - because you have distinguish between whether you're using it as a topic marker (use は) or as something else (use わ). On the other hand, you never have to wonder how to write the sound *'ha'* - it's always written は. :idea: こんにちは is written with a は because the は is actually a topic marker - こんにち literally means "THIS-DAY"!! So, literally, when you say こんにちは you're saying "THIS DAY IS..." :P -Sayaka :P

さやかさん、　ありがとう　

どういたしまして。 You are very welcome. :P