What is the rule for ch making k sound as in beginning of chamomile?

The rule for "ch" making a "k" sound at the beginning of words like "chamomile" is that it's derived from Greek.

Here's a breakdown:

* Greek Roots: Many words with "ch" making a "k" sound come from Greek words where the letter "χ" (chi) was used.

* Pronunciation Shift: When these Greek words were adopted into English, the "χ" sound (which is similar to "kh") changed to a "k" sound.

Examples:

* Chameleon: From the Greek "khamaileon"

* Chaos: From the Greek "khaos"

* Character: From the Greek "kharakter"

* Chorus: From the Greek "choros"

Important Note:

This rule is specific to words with the "ch" at the beginning. In many other words, "ch" makes a "ch" sound as in "chair" or a "sh" sound as in "machine."