「くん」は親しい男子、「ちゃん」は親しい女子につけるって英語でなんて言うの？

Honorifics are words that express respect. "-kun" refers to boys or men you are close to and "-chan" is for girls or women you are close to.

Honorifics are words used to show respect to someone or show closeness to a person. For most Asian countries, honorifics are used closely with a person's name.

Friend: What does "-kun" and "-chan", mean?
You: It's an honorific for boys and girls we are friends or are close with. "-Kun" is used for boys while "-chan" is used for girls.

Example: Good morning, Kei-kun./ Good morning, Yuri-san.

"An a sign of respect we say Kun after a boys name and Chun after a girls name." This explains to the person that by saying Kun after a boys name and Chun after a girls name you are showing respect.

We use San after the name of an adult.

As other posters have explained, these type of words or syllables are called "honorifics", like "Mr." in English.

If you call it a "suffix", then it is clear to the person that you are talking to that the syllable comes AFTER the word to which it refers, not before.

The opposite of "suffix" is "prefix", that is, one syllable or more that you put BEFORE a word, not after.

Some languages (like Turkish) have syllables you put in the middle of a word. This is called an "infix". But English DOESN'T really have these -- thank God! English is already too difficult!

You can explain it in the following way:
-"Kun" is an honorific attached to a boy's name and "chan" to a girl's name.

*Kun is used after a boy's name an chan after a girl's name as a sign of respect.- This means that you use kun and chan as a way to respect other people.
A:Kun is used after a boy's name an chan after a girl's name as a sign of respect.
B:Oh that is nice
A: For example John Kun or Sofia Chan

Explanation: MASTER is the title given to a boy, and MISS is the title given to s girl in the UK, though neither are common in casual speech.
Example sentence:
"Miss Wood is waiting for you at reception."