Learn Dutch: Deze grote ramen verlichten de zolder perfect. - These large windows illuminate the attic perfectly.

The prefix ver- often turns an adjective or a noun into a verb that means "to make [adjective]" or "to cause a change of state". Here, it attaches to the word licht (light). So, verlichten literally means "to make light" or "to illuminate".

Does verlichten only mean "to illuminate", or are there other meanings?

It has another very common meaning! Because the base word licht can also mean "light" in terms of weight (not heavy), verlichten is frequently used to mean "to relieve" or "to alleviate". For example, you can use it when talking about relieving pain (de pijn verlichten) or lightening a heavy burden.

Why does grote have an -e ending while perfect does not?

grote is an adjective placed directly in front of the noun it modifies, ramen (windows). Because ramen is plural, the adjective must take the -e ending. On the other hand, perfect is acting as an adverb here because it describes how the windows illuminate the attic, rather than describing a noun. In Dutch, adverbs do not take an -e ending.

Why does the word for "large" lose an o when it is written as grote?