In any language a word can have different meanings.
Let's look at the PTS's dictionary definition:
Pali Text Society wrote:Sangha [fr. saŋ+hṛ; lit. "comprising." The quâsi pop. etym. at VvA 233 is "diṭṭhi -- sīla -- sāmaññena sanghāṭabhāvena sangha"] 1. multitude, assemblage Miln 403 (kāka˚); J i.52 (sakuṇa˚); Sn 589 (ñāti˚); 680 (deva˚); D iii.23 (miga˚); Vv 55 (accharā˚=samūha VvA 37). bhikkhu˚ an assembly of Buddhist priests A i.56, etc.; D i.1, etc.; S i.236; Sum i.230, 280; Vin i.16; ii.147; bhikkhunī˚ an assembly of nuns S v.360; Vin i.140; sāvaka˚ an assembly of disciples A i.208; D ii.93; S i.220; PvA 195, etc.; samaṇa˚ an assembly of ascetics Sn 550. -- 2. the Order, the priesthood, the clergy, the Buddhist church A i.68, 123, etc.; D i.2, etc.; iii.102, 126, 193, 246; S iv.270 sq.; Sn 227, etc.; J ii.147, etc.; Dhs 1004; It 11, 12, 88; Vin i.102, 326; ii.164, etc. <-> 3. a larger assemblage, a community A ii.55=Sv.400; M i.231 (cp. gaṇa). -- On the formula Buddha, Dhamma, Sangha see dhamma C 2.
- http://dsal.uchicago.edu/cgi-bin/philol ... :2839.pali
So a Sangha could be a group of ordained Monks, Nuns, or it could be a large lay community.
If you got a bunch of lay people together and called yourself a Sangha you might recieve some politely worded letters though
"And so, because this Teaching is so different from what Westerners are accustomed to, they will try to adapt the Teaching to their own framework. What they need to learn to do is not to adapt the Teaching to their own point of view but to adapt their own point of view to the Teaching. This is called saddhá, or faith, and it means giving oneself to the Teaching even if the Teaching is contrary to one’s own preconceived notions of the way things are."- Ven BodhesakoNanavira Thera's teachings - An existential approach to the Dhamma
| Ven. Bodhesako's essay on anicca