Definition:Theta Notation/Also known as

$\Theta$ Notation: Also known as
Some sources refer to $\Theta$ notation as big-$\Theta$ notation, in parallel with big-$\OO$ and big-$\Omega$.

However, it is worth bearing in mind that:
 * There is no Little-Theta Notation

and so there is no need to distinguish between big-$\Theta$ and little-$\theta$.

Hence consistently use the term $\Theta$ notation, voicing it as theta notation.