Editing Openai/68fceef0-7248-8013-bf5d-581461dec5bc (section)

===== Defined by the arc length per tooth on the pitch circle =====
Example: 0.314 in circular pitch, etc.
Used when people don’t want DP or module, but a direct linear pitch value.

Those three are the usual distinctions people think of when talking about “different types of pitch.”

Most U.S.-built racks and pinions in catalogs will be listed in DP or Module.
Cycloidal/involute/etc. was a different distinction (tooth form) — but your memory sounds like DP vs Module vs Circular Pitch.

If you want, the webpage can allow the user to pick one of these as the pitch input mode:
* DP (imperial default)
* Module (metric only if needed — can be hidden by default)
* Circular pitch (optional/uncommon)

Reply with one word so I know how to proceed:
* “DP only”
* “DP + Module”
* “DP + Module + CP”