Here are some examples:
* Filament: A thin thread or fiber.
* Filigree: Ornamental work made with fine wire or thread.
* Filature: A place where silk is spun or reeled.
* Filum: A thread-like structure, often used in biological contexts.
It's important to note that "fil" is not a standalone word in English. It's a root that combines with other prefixes and suffixes to create new words.