The most common Quenya word for “sea”, derived from the root √GAYAR (or sometimes √AYAR), where the vowel combination was the result of the frequent Quenya sound change whereby aya > ëa.
Note that Quenya does not use the definite article before unique individual things like the Sun and the Moon. Likewise ëar “the sea” is almost never used with the definite article, only in the case where one is indicating a specific definite sea among a group of seas already under discussion, which is a rare occurrence.
Conceptual Development: As an element in the name ᴱQ. Earendel, this word first appeared as ᴱQ. ea or ᴱQ. earen “eagle” (QL/34). But by the 1940s Tolkien changed the form and meaning of this name to ᴹQ. Earendil “Friend of the Sea” (SD/237), and the word ᴹQ. ear “sea” appeared in The Etymologies of the 1930s as a derivative of ᴹ√AYAR (Ety/AY). In The Notion Club Papers of the 1940s it had the form eare and the gloss “open sea” (SD/241, 305). The first appearance of the “sea” meaning of this word seems to be in a word-list associated with the Ambarkanta “Shape of the World” from the early 1930s, where ear had the glosses “water, sea” (SM/241), though in later writings only “sea” remained.
ëar noun "sea" (AYAR/AIR [gives also dat. sg. ëaren],WJ:413; see Letters:386 for etymology). Not to be confused with the pl. form of the verb ëa "be, exist". Pl. ëari "seas" (FS, LR:47); Eär "the Great Sea" (cf. ëaron "ocean"), ablative Eärello "from the Great Sea", et Eärello "out of the Great Sea" (EO). Eärë noun "the open sea" (SD:305). Compound ëaruilë noun "seaweed" (UY). Found in proper names like Eärendil "Sea-friend", Eärendur masc. name, *"Sea-servant"; in effect a variant of Eärendil(Appendix A). Eärendur was also used ="(professional) mariner" (Letters:386).Fem. name Eärwen "Sea-maiden" (Silm); Eärrámë "Sea-wing", "Wings of the Sea", name of Tuor's ship (RAM, AYAR/AIR, SA)