Word 1: Rain (RAYN)
Meaning 1. Water falling in drops condensed from vapor in the atmosphere.
Example Sentence: It has been raining incessantly for the last three days.

Meaning 2: A heavy or abundant fall.
Example Sentence: bounties rain in thousands when the time is right.

Word 2: Reign (RAYN)
Meaning 1: The period during which a monarch is the official ruler of a country.
Example Sentence: Queen Elizabeth II has been reigning over the United Kingdom since her accession in 1952.

Meaning 2:To hold the title of monarch, but with limited authority.
Example Sentence: The state is put under the reign of an eligible person if the king to be is a minor.

Meaning 3: To be predominant or prevalent.
Example Sentence: There was a reign of confusion after the workers called off their strike.

Word 3: Rein (RAYN)
Meaning 1: A restraining influence.
Example Sentence: A number of measures have been taken by the authorities to rein in inflation.

Meaning 2: Unhampered opportunity.
Example Sentence: Students were given free rein to express their ideas.

Meaning 3: A strap fastened to a bit by which a rider or driver controls an animal.
Example Sentence: He drew the rein and tethered the horse to the pine tree.

Meaning 4: To stop or slow up one’s horse or oneself by or as if by pulling the reins.
Example Sentence: She normally held her emotions in tight rein.

Example Sentence using all the words:
He reined his temper and went to visit the new ruler in the heavy rain.