According to Genesis, the ark had a window in addition to its side door. Genesis 6:16 instructs Noah to make an opening for the ark and to finish it within a cubit of the top; later, Genesis 8:6 describes Noah opening the window.
English translations differ slightly in how they describe this feature. Some say “window,” while others use “opening” or a term related to light. The passage also mentions a door in the side, so the text clearly distinguishes the two features.
The window becomes important near the end of the Flood account. Noah opens it before sending out the raven and the dove, using the birds to learn whether the waters have receded. The narrative therefore gives the opening a practical role as well as mentioning it in the construction instructions.
This detail is often replaced in illustrations by multiple portholes or a large roof opening. Those artistic choices are not specified by Genesis. The safest textual answer is the singular window or opening described near the top of the ark.