IPA: /nɒkˈtɜːnəli/
KK: /nɑkˈtɜrnəli/
In a manner that occurs or is active during the night.
Some animals are nocturnally active, meaning they hunt and feed at night.
Nocturnally → It is formed from "nocturnus" (from Latin, meaning of the night) and the suffix "-ally" (meaning in a manner relating to). The word "nocturnally" means in a manner that relates to or occurs during the night.
Think of 'nocturnus' which relates to the night, and remember that 'nocturnally' describes something that happens during the night.