“buy and hold” investment
$$ HPR_t = \frac{P_t+D_t+P_{t-1}}{P_{t-1}} $$
Where:
$P_t$ is investment value at end of holding period.
$P_{t-1}$ is initial investment value.
$D_t$ is the investment income such as dividend, coupon, etc.
Lets denote this period return as r.
Now assume we have a sample of returns over multiple T periods for a single asset $(r_1, r_2, r_3, ..., r_t)$
Average returns over time-series:
Arithmetic Average Return, Geometric Average Return
(check book for formulas and examples)