per, each

The Latin word per is encountered in phrases such as per diem, per capita and per cent.

• The sales staff are allowed the usual per diem (daily) rate.

Per is also used for scientific, financial and business writing, and for expressing ratios.

• In water analysis, bacteria are counted in parts per million.
• The high-tech firm indicated gains of eight cents per share in the second quarter.

In general writing, the traditional guideline was that per should not be used before an English word in place of each or a, because it was unfamiliar and less idiomatic; however, that objection is no longer valid.

• Carlos and Ken paid $12 each (or $12 per person) to rent skates for the afternoon.

• The speed limit on that secondary road is 80 kilometres an hour (or per hour).

Since per means “for each,” it is redundant to write per each.

• The basketball coach allotted two uniforms for (not per) each player.
• The basketball coach allotted the players two uniforms each.