Identify the missing term in the following number series:
11, 22, 44, 66, ?

The given series consists of multiples of $11$:
* $11\times 1=11$
* $11\times 2=22$
* $11\times 4=44$
* $11\times 6=66$

Looking at the differences between the consecutive numbers:

* $22-11=11$
* $44-22=22$
* $66-44=22$

Apart from the first step, the difference between consecutive terms becomes a constant addition of $+22$:

$$66+22=88$$

Alternatively, the multipliers are $1$, and then consecutive even numbers $2,4,6,8$. Thus, $11\times 8=88$.