Occitano-Romance languages

• Both Varieties of Catalan and Occitan have apocope on terminal latin vowels -Ĕ, -Ŭ (protoromance -e, -o):

Latin		Catalan		Occitan		Castilian
Orthography	IPA	Orthography	IPA	Orthography	IPA
TRŬNCŬM	[ˈt̪rʊŋ.kʊ̃ˑ]	tronc	[tɾoŋ(k)]	tronc	[tɾoŋ(k)]	tronco
LĬGNOSŬM	[ˈlʲɪŋ.n̪ɔ.sʊ̃ˑ]	llenyòs	[ʎəɲós]	lenhós	[leɲús]	leñoso

This evolution does not occur when the ellision of -e or -o results in a terminal consonant cluster.

Latin	Old Occitan	Catalan	Occitan
ÁRBORĔ	ARBRE	arbre	arbre
QUATTUOR	QUÁTRO	quatre	quatre

• A large part of the lexicon is shared, and in general written words in Catalan and Occitan are mutually intelligible. Similar to the differences in lexicon between Portuguese and Castilian (although this is not always the case with spoken language and varies from dialect to dialect). There are also notable cognates between Catalan, Valencian, Occitan and Aragonese.

English	Latin	Occitan	Catalan	Aragonese
old	VÉC(U)LA	vielha	vella	viella
middle / half	MEDIU(M)	mièg	mig	meyo
I	EGŌ	ieu ~ jo	jo	yo
to follow	SEQUĔRE	seguir ~ siegere	seguir	seguir(e)
leaf	FŌLIA(M)	fuòlha ~ fuèlha	fulla	fuella ~ folla

Most of the differences of the vowel system stem from neutralizations that take place on unstressed syllables. In both languages a stressed syllable has a great number of possible different vowels, while phonologically different vowels end up being articulated in the same way in an unstressed syllable. Although this neutralization is common to both languages, the details of the differ markedly. In Occitan the form of neutralization depends on whether a vowel is pretonic (before the stressed syllable) or postonic (after the stressed syllable). For example /ɔ/ articulates as [u] in pretonic position and as [o] in postonic position, and only as [ɔ] in stressed position. In contrast neutralization in Catalan is the same regardless of the position of the unstressed syllable (although it differs from dialect to dialect). Many of these changes happened in the 14th or late 13th century.

Slightly older are the palatalizations present in Occitan before a palatal or velar consonant:

Variations in the spellings and pronunciations of numbers in several Occitano-Romance dialects:[9][10]

Numeral	Occitan					Catalan		Aragonese[11]	PROTO- OcRm
	Northern Occitan		Western Occitan	Eastern Occitan		Eastern Catalan	Northwestern Catalan
	Auvergnat	Limousin	Gascon	Languedocien	Provençal
1	vyn / vynɐ vun / vunå	ỹ / ynɔ un / una	y / yo un / ua	ỹ / yno un / una	yŋ / yno un / una	un / unə un / una	un / una un / una	un~uno / una un~uno / una	*un / *una
2	du / dua dou / duas	du / dua dos / doas	dys / dyos dus / duas	dus / duos dos / doas	dus / duas dous / douas	dos / duəs dos / dues	dos dos / dues	dos / duas dos / duas	*dos~dus / *duas
3	tʀei trei	trei tres	tres tres	tres tres	tʀes tres	trɛs tres	trɛs tres	tɾes tres	*tres
4	katʀə catre	katre quatre	kwatə quatre	katre quatre	katʀə quatre	kwatrə quatre	kwatre quatre	kwatro~kwatre quatro / quatre	*kwatre
5	ʃin sin	ʃin cinc	siŋk cinq	siŋk cinq	siŋ cinq	siŋ / siŋk cinc	siŋ / siŋk cinc	θiŋko~θiŋk cinco / cinc	*siŋk
6	ʃei siei	ʃiei sieis	ʃeis sheis	siɛis sièis	siei sieis	sis sis	sis sis	seis~sieis seis / sieis	*sieis
7	se sé	ʃe sèt	sɛt sèt	sɛt sèt	sɛ sèt	sɛt set	sɛt set	siet~sɛt siet / set	*sɛt
8	vø veu	jɥe uèch	weit ueit	ɥeʧ uèch	vɥe vue	buit / vuit vuit	vuit / wit vuit / huit	weito~weit ueito / ueit	*weit
9	niø~nou nieu~nou	nɔu nòu	nau nau	nɔu nòu	nu nòu	nɔu nou	nɔu nou	nweu~nɔu nueu / nou	*nɔu
10	die~de dié~dé	diɛ~de detz	dɛʦ dètz	dɛʦ dèts	dɛs dès	dɛu deu	dɛu deu	dieθ~deu diez / deu	*dɛʦ

The numbers 1 and 2 have both feminine and masculine forms agreeing with the object they modify.