In the Etymologies, the word for "bread" is given as bast , Quenya masta, but it seems that Tolkien later changed his mind and updated the word to bass, as shown in Quenya massánie, Sindarin besain, besoneth "bread-giver", and in the mutated form (i)mbas (apparently prefixed with the article). These latter Sindarin forms are however dubious, as we would rather have expected bessain (as a regular cognate of Quenya massánie) and bassoneth (without i-affection), and possibly a different mutation pattern after the article
Sindarin
bas(t)
noun. bread
bass
noun. bread
bassoneth
noun. bread-giver
See bass for a discussion regarding this word
besain
noun. bread-giver
See bass for a discussion regarding this word
besoneth
noun. bread-giver
See bass for a discussion regarding this word
bessain
noun. bread-giver
See bass for a discussion regarding this word
lembas
noun. journey bread made by the Elves
besain
noun. the Lady, breadgiver
In notes from the 1950s Tolkien said the word besain was a title for noble Elf ladies as the provider of lembas, the equivalent of (and probably adapted from) Q. massánië, literally “bread giver [giving]” (PM/404). It was likely coined based on the historical developments of this name: ✱mbassānye > (m)bessenı̯ > bessein > besain. Christopher Tolkien noted that his father wrote oneth above -ain, indicating an alternate form, which Christopher Tolkien wrote as ✱besoneth (PM/405). However, I think it is likelier the alternate would be ✱basoneth = S. bas “bread” + oneth “✱giver [f.]”, because in this alternate form there would be no reason for the initial element bas- to undergo i-affection.
ledhbas(t)
noun. waybread
bass
bread
bass (i mass, o mbass, construct bas), pl. bais (i mbais). The sg. form with article "imbas" in VT44:23 may be seen as archaic Sindarin, for later *i mas(s) as suggested here. In ”Noldorin”, the word for "bread" was bast (LR:372 s.v. MBAS), but otherwise it would have the same mutations.
bass
bread
(i mass, o mbass, construct bas), pl. bais (i mbais). The sg. form with article "imbas" in VT44:23 may be seen as archaic Sindarin, for later ✱i mas(s) as suggested here. – In ”Noldorin”, the word for "bread" was bast (LR:372 s.v. MBAS), but otherwise it would have the same mutations.
bassoneth
bread-giver
(fem.) bassoneth (lady) (i massoneth, o mbassoneth), pl. bassonith (i mbassonith). Archaic *bassauneth. Also bessain (i messain, o mbessain), no distinct pl. except with article (i mbessain)
bassoneth
bread-giver
bassoneth (lady) (i massoneth, o mbassoneth), pl. bassonith (i mbassonith). Archaic *bassauneth.
bassoneth
bread-giver
(lady) (i massoneth, o mbassoneth), pl. bassonith (i mbassonith). Archaic ✱bassauneth. Also bessain (i messain, o mbessain), no distinct pl. except with article (i mbessain)
lembas
way-bread, journey-bread
pl. lembais.
basoneth Reconstructed
noun. breadgiver
bassoneth
lady
(bread-giver) (i massoneth, o mbassoneth), pl. bassonith (i mbassonith). Archaic ✱bassauneth.
heryn
lady
1) heryn (i cheryn, o cheryn), no distinct pl. form, not even with article (i cheryn), 2) hiril (i chiril, o chiril), no distinct pl. form even with article (i chiril), coll. pl. hirillath. 3) brennil (i vrennil), pl. same as sg. except with article: i mrennil. Coll. pl. brenillath. 4) bassoneth (bread-giver) (i massoneth, o mbassoneth), pl. bassonith (i mbassonith). Archaic *bassauneth. 5) dî (i nî, o ndi) (bride), no distinct pl. form except with article (i ndî).
cram
noun. cake of compressed flour or meal (often containing honey and milk)
heruin
noun. lady
heruin
noun. lady
heryn
noun. lady
heryn
noun. lady
heryn
noun. lady
hiril
noun. lady, lady; [G.] princess, †queen
rodel
lady
1a _n._lady, high lady. >> Nimrodel
brennil
lady
(i vrennil), pl. same as sg. except with article: i mrennil. Coll. pl. brenillath.
cram
cake
(of compressed flour or meal, often containing honey and milk, for use on long journeys) cram (i gram, o chram), pl. craim (i chraim), coll. pl. crammath
cram
cake
(i gram, o chram), pl. craim (i chraim), coll. pl. crammath
dî
lady
(i nî, o ndi) (bride), no distinct pl. form except with article (i ndî).
heryn
lady
(i cheryn, o cheryn), no distinct pl. form, not even with article (i cheryn)
hiril
lady
(i chiril, o chiril), no distinct pl. form even with article (i chiril), coll. pl. hirillath.
This was the word for “bread” in Sindarin and its conceptual precursors for much of Tolkien’s life, derived from the equally long-lived root √MBAS “bake”. The word dates all the way back to the Gnomish Lexicon of the 1910s where G. bast “bread” was derived from the early root ᴱ√M(B)ASA “cook, bake” (GL/22). ᴱN. bast “bread” reappeared in Early Noldorin Word-lists of the 1920s (PE13/138) and appeared again as N. bast “bread” in The Etymologies of the 1930s under the root ᴹ√MBAS “knead” (Ety/MBAS).
It appeared without a final t in the Sindarin version of the Lord’s Prayer from the 1950s: anno ammen sír imbas ilaurui vín “give us this day our daily bread” (VT44/21). However the t was restored in the phrase penim vast “we have no bread” from around 1959 (PE17/144). The late vacillations on the presence and absence of t are likely connected to Tolkien challenges with the derivation of lembas; see that entry for discussion. Likewise, the mutated forms mbas vs. vast indicate some late uncertainty on whether the primitive form began with mb- or b-.
Neo-Sindarin: For purposes of Neo-Sindarin, I would assume the normal form was bast “bread” from ancient mbasta, so that lenited forms show m(b)-. However, I would assume there is a variant bas(s) [< ✶mbassē] that appears occasionally in compounds like lembas.