Well, I would rather focus on the different shades of meaning of this word and use the prefix ú- (cf. úlann, úvelui, etc.) as a Joker in Sindarin. :)

simple = unusual, not special

*úvinai, *ú-orchal

simple = not hard to do

*údhir, *úranc = athgar

simple = not complicate

*úremmen

In the sense 'ordinary, not special' one may consider Q. *haimea; in the sense 'easy' one gets Q. *askare, *askárima; in the sense 'basic, not derived or put together' one may consider Q. essea '?primary' or setya, setta 'first, ?primary' (a deleted word, but still).

As the primary meaning of asta is 'division', 'one of several equal parts', perhaps *alastea (or *úastea) could be used for 'simple' = 'without division', 'undivided', 'not compound'.

Those are all excellent suggestions, thank you.

(Now on to the next question: how would you say 'suggest, propose'? :))

That's simple! :)

S gor-, Q or- (√ӠOR)

How about tyasta- 'put to the test' (QL)?

Eteminya! Thanks, all.

+Björn Fromén As far as Greco-Roman metaphors go, 'dividing' is rather 'analyzing': 'science' is related to scindō 'cut, divide', 'analysis' is from lyō 'release, unfasten'.
'Complex' is literally 'weaved together'; in Russian сложный is 'put together', but I'm not sure it's not a calque.

In Hungarian 'simple' is egyszerű, which is literally 'like one', where egy is 'one' and -szerű is a suffix more or less corresponding to the Qenya case ending -ndon.

For "suggest", maybe *et+orta-[1] or something similar (vs. e.g. /quetë rá/ +Dat).

Many real-world languages use a prefixed verb, even though the "European frequenter" in Italian /proporre/ & Russian /пред|лагать/ is certainly contrasted by Classical Latin /admoneo/ and /in-, sub-icio/.

The etymology of Finnish /ehdottaa/ is unclear.
http://en.wiktionary.org/wiki/ehto

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[1] compare the partly similar Icelandic phrase /stinga upp á/ (recalled as an afterthought)

If */ompata-/ (or other correctly formed caus/tr verb from OPO) can represent English "promote, advance", then that would make a useful half-synonym.

Another word that is difficult to pin down is 'counsel, advice, bid'. Looking through the Gnomish and Qenya Lexicons couldn't see any immediate solutions.

According to "Notes on Óre" (VT 41) Q or-, S gor- "could be used of the influence of one person upon another by visible or audible means (words or signs) -- in which case 'counsel' was nearest to its sense". No example is given, but presumably it takes this meaning when construed with a personal subject: *meldonyar orir nin caritas 'my friends counsel me to do it' (contrast the impersonal ore nin caritas 'I feel an urge to do it').

I like or- more and more-it's taking on biblical proportions much alike OE raedan or bidan.