# Why is 'the period' marked as letter T?

I'm not a native English speaker and I was wondering, why 'the period' got the letter $T$. I've asked myself the question when I was thinking about stuff related to the frequency. I.e.:

• $f$ - frequency
• $v$ - velocity of a wave
• $a$ - acceleration

all of those have 'generic' markings, but not 'the period'. Was the letter $T$ used to somehow relate to 'time' the period describes? (I just need an acknowledgement really)

• I agree with you conclusion about $t$ and time, but I'll let native English speaker to confirm it as an answer. – Pygmalion May 14 '12 at 16:34
• I think so - it seems nicely symmetric since in many equations you would write something like $x=\sin(\frac{t}{T})$ - the time variable t increases until it gets to big T, then things repeat. – user2963 May 14 '12 at 16:50

Hmm, what if they thought about it this way: Let's put t for time (latin: tempus) and since time and period are connected (I would think of the period as the smallest time a cyclic phenomena requires to complete one full cycle) let's just denote period with T as t is already taken.

• Yes, this looks like a logical move (bc why time got the letter t if T (period) is already derived from 'tempus'). I'll mark your answer as the correct one. – colemik Jul 3 '12 at 15:04

I'd say it's form latin tempus - http://la.wikipedia.org/wiki/Frequentia

• +1 This sounds reasonable, as in time physics was starting, Latin was lingua franca in all of the sciences. – Pygmalion May 14 '12 at 17:25

Indeed, a number of websites suggest that the T for period is for time.

Wikipedia: The period, usually denoted by T, is the length of time taken by one cycle, and is the reciprocal of the frequency f: