A lecture can be a talk for instruction given to an audience or class.
A lecture can also be a warning or telling off
"Leisure, philosophy, or place where lectures are given."
There is no standard collective noun for the noun lectures, in which case a noun suitable for the situation is used; for example, a series of lectures, a program of lectures, a yawn of lectures, etc.
you can download lectures from internet
she'd miss her lectures
Hulsean Lectures was created in 1820.
Tarner Lectures was created in 1916.
Fashionable Lectures was created in 1872.
Lectures on Faith was created in 1835.
Gifford Lectures was created in 1898.
Donnellan Lectures was created in 1794.
Guildhall Lectures was created in 1959.
Warburton Lectures was created in 1768.