Araknoid

Araknoid is a term used as a variant spelling of arachnoid in some sources and can refer to several related concepts in science and fiction.

In anatomy, araknoid commonly denotes the arachnoid mater, the delicate, spider‑web‑like middle membrane of the meninges that enclose the brain and spinal cord. The arachnoid lies between the dura mater (outer) and the pia mater (inner). The subarachnoid space, located beneath the arachnoid, contains cerebrospinal fluid and blood vessels. Arachnoid trabeculae cross the space to connect the arachnoid with the pia, helping cushion the brain and form a barrier known as the arachnoid barrier layer, part of the blood–CSF barrier. Common pathologies include arachnoid cysts, arachnoiditis, and conditions affecting cerebrospinal fluid flow.

Outside medicine, araknoid appears in science fiction and fantasy as a name or descriptor for spider‑like beings or creatures, or for technologies and organisms inspired by arachnid motifs. In such uses, the term is typically chosen to evoke a spider‑related appearance or theme rather than a specific anatomical meaning.

Etymology: derived from Greek arachne, “spider,” with the suffix -oid meaning “resembling.”

See also: arachnoid mater, meninges, subarachnoid space, arachnoiditis.