Pholcidae, commonly known as cellar spiders, are a spider

Spider

Spiders are air-breathing arthropods that have eight legs, and chelicerae with fangs that inject venom. They are the largest order of arachnids and rank seventh in total species diversity among all other groups of organisms...

 family in the suborder Araneomorphae

Araneomorphae

The Araneomorphae are a suborder of spiders. They are distinguished by having fangs that oppose each other and cross in a pinching action, in contrast to the Mygalomorphae , which have fangs that are nearly parallel in alignment.- Distinguishing characteristics :Note the difference in the...

.

Some species, especially Pholcus phalangioides

Pholcus phalangioides

The cellar spider or daddy longlegs , also known as the skull spider due to its cephalothorax looking like a human skull, is a spider of the family Pholcidae. Females have a body length of about 9 mm; males are slightly smaller. Its legs are about 5 or 6 times the length of its body...

, are commonly called granddaddy long-legs spider, daddy long-legs spider, daddy long-legger, or vibrating spider. Confusion often arises because the name "daddy long-legs

Daddy Long-legs

Daddy-Long-Legs is a 2005 South Korean romance film. It features a cameo by Hyun Bin. It was one of four Korean movies screened at the 2006 International Fajr Film Festival in Iran. The story is loosely inspired by the novel Daddy-Long-Legs by Jean Webster.-Plot:Young-mi , is a young woman who has...

" is also applied to two distantly related arthropod

Arthropod

An arthropod is an invertebrate animal having an exoskeleton , a segmented body, and jointed appendages. Arthropods are members of the phylum Arthropoda , and include the insects, arachnids, crustaceans, and others...

 groups: the harvestmen

Opiliones

Opiliones are an order of arachnids commonly known as harvestmen. , over 6,400 species of harvestmen have been discovered worldwide, although the real number of extant species may exceed 10,000. The order Opiliones can be divided into four suborders: Cyphophthalmi, Eupnoi, Dyspnoi and Laniatores...

 (which are arachnid

Arachnid

Arachnids are a class of joint-legged invertebrate animals in the subphylum Chelicerata. All arachnids have eight legs, although in some species the front pair may convert to a sensory function. The term is derived from the Greek words , meaning "spider".Almost all extant arachnids are terrestrial...

s but not spiders), and crane flies

Crane fly

A crane fly is an insect in the family Tipulidae. Adults are very slender, long-legged flies that may vary in length from though tropical species may exceed to ....

 (which are insect

Insect

Insects are a class of living creatures within the arthropods that have a chitinous exoskeleton, a three-part body , three pairs of jointed legs, compound eyes, and two antennae...

s).
Pholcids are fragile spiders, the body being 2–10 mm in length with legs which may be up to 50 mm long.