When is は (ha) pronounced as (wa) like in こんにちは?

The particle "は" (pronounced "ha") is usually used as a grammatical marker to indicate the topic of a sentence in Japanese. However, when it is used as a particle in a sentence, it is pronounced as "wa" instead of "ha". This pronunciation change happens for historical reasons and is just a phonetic rule in the Japanese language.

To understand when "は" is pronounced as "wa," you need to know about the topic marker function. In Japanese, the topic of a sentence is often placed at the beginning or before the verb, and the particle "は" is used to mark this topic. It is never used to denote possession or any other meaning besides indicating the topic.

For example:
- こんにちは (konnichiwa): The word "こんにちは" is a common Japanese greeting meaning "good day" or "hello." Here, the particle "は" is used as a topic marker, and it is pronounced as "wa" to indicate that the word itself is the topic being addressed.
- 私は学生です (watashi wa gakusei desu): In this sentence, "私は" (watashi wa) means "as for me" or "I," and it functions as the topic of the sentence. Again, "は" is pronounced as "wa" to mark the topic.

Remember that when "は" is used as a particle, it is always pronounced as "wa." In other cases, such as when it is used as part of a word or to indicate the "ha" sound, it is pronounced as "ha."