Oe Symbol (œ Œ): The Joined o and e French Spelling Needs

Does French require œ, or is oe enough?

French requires the oe symbol. Writing coeur for cœur is a spelling shortcut, not a second correct form. The OQLF, the Québec office for the French language, is plain about it in its note on the double letters æ and œ (opens in a new tab). In œuvre, cœur or Œdipe, the joined vowels must never be separated, in small letters or in capitals.

The Académie française shows the same rule by example. Its dictionary, in the ninth edition dated 2024, prints the headwords CŒUR (opens in a new tab), SŒUR (opens in a new tab) and ŒUF (opens in a new tab) with the ligature, capitals included.

The rule cuts both ways: joining the wrong pair is also a mistake. The OQLF names words where the two vowels sit side by side but stay apart. Wiktionary's entries for coexister (opens in a new tab) and moelle (opens in a new tab) add the detail in the last column.

Word	Joined or apart?	What keeps it that way
cœur, sœur, œil, nœud, vœu	joined: œ	listed by the OQLF among the words written with œ
œsophage, œnologie, œdème	joined: œ	the same OQLF list, learned words
coexistence, coexister	apart: oe	in the OQLF list of pairs that stay separate; Wiktionary splits coexister into co- and exister
moelle	apart: oe	in the OQLF list of pairs that stay separate; Wiktionary marks mœlle as nonstandard
Groenland, goéland, Noël	apart: oe, oé, oë	in the same OQLF list of separate pairs

Place names keep the joined letter too, as the French towns in the place data on this page show, such as Marcq-en-Barœul.

How is œ pronounced in a French word?

The oe ligature has no single sound. For œ pronunciation, the letter that follows it decides. The OQLF's note on pronouncing the double letter œ (opens in a new tab) gives the rule, with a transcription for every example.

What comes after œ	How œ sounds	OQLF examples
a consonant	[e], the é of et	fœtus [fetys], œnologie [enɔlɔʒi], Œdipe [edip], œcuménique [ekymenik]
the letters st	[ɛ], the è of haie	œstrogène [ɛstʁɔʒɛn]
u or i, with the syllable going on	[œ], the eu of neuf	sœur [sœʁ], bœuf [bœf], œil [œj], manœuvre [manœvʁ]
u, closing the spoken syllable	[ø], the eu of eux	nœud [nø], vœu [vø], œufs [ø]

The last two rows explain a puzzling pair. One egg is un œuf, said [œf]. Several eggs are des œufs, said [ø]. The Académie's entry notes that the f is not pronounced in the plural. Wiktionary's entry for œufs (opens in a new tab) gives the same [ø] and lists eux as a homophone.

The OQLF also flags a common slip. Before a consonant, œ should not be said as eu. So œnologie is [enɔlɔʒi], not [ønɔlɔʒi], and Œdipe is preferably [edip]. Wiktionary's entry for œsophage (opens in a new tab) records that eu reading as common but proscribed. The OQLF allows one exception: œrsted and œrstite are said with [ø].

Why do cœur and œsophage both have an œ?

They have it for different reasons. In the everyday words, the oe symbol spells a French vowel. The Latin source of each word had no oe at all. In the learned words, œ stands where Greek wrote the pair οι.

The Académie's etymologies show the first group. Cœur comes from Latin cor and was written cuer in the eleventh century. Sœur comes from soror. Œuf comes from ovum and was written of in the twelfth century. So the oe ligature French uses in these words was not inherited from Latin.

Word	Where it comes from	Did the source word have oe?	How French says the œ
cœur	Latin cor, through Old French cuer	no	[œ]
sœur	Latin soror	no	[œ]
œuf	Latin ovum, through Old French of	no	[œ], and [ø] in œufs
Œdipe	Latin Oedipus, from Greek Οἰδίπους	yes: Latin oe for Greek οι	[e]
œsophage	Greek οἰσοφάγος	yes: Greek οι	[e]
fœtus	Latin fētus	no: a mistaken oe that stuck	[e]

The first three rows follow the Académie entries linked above. The rest follow Wiktionary's entries for œsophage, Oedipus (opens in a new tab) and fœtus (opens in a new tab). The fœtus row is the odd one. Wiktionary calls the oe spelling a hypercorrection that already shows up in Latin, where foetus sat beside the original fētus. French still writes fœtus, and the rarer fétus is closer to the Latin.

The pattern matches the pronunciation rule. In cœur, sœur and œuf, a u follows the œ, and it sounds like eu. In the Greek words, and in fœtus, a consonant follows, and œ sounds like é.

Is the IPA symbol œ the same sound as ø?

No. They are neighbours on the vowel chart, one step apart in height. The IPA chart (opens in a new tab) of the International Phonetic Association places ø among the close-mid front vowels and œ one row lower, among the open-mid ones. Both are rounded. A third symbol, ɶ, sits at the bottom of the chart.

IPA symbol	Its row on the IPA chart	Unicode name	A French word with the sound
ø	close-mid front rounded	U+00F8 LATIN SMALL LETTER O WITH STROKE	nœud [nø], eux
œ	open-mid front rounded	U+0153 LATIN SMALL LIGATURE OE	sœur [sœʁ], neuf
ɶ	open front rounded	U+0276 LATIN LETTER SMALL CAPITAL OE	none in the OQLF notes

The Unicode names come from UnicodeData.txt (opens in a new tab). The IPA Extensions chart (opens in a new tab) describes ɶ as a low front rounded vowel and points back to œ. The Latin Extended-A chart (opens in a new tab) lists French and IPA among the uses of œ, along with Old Icelandic and Old English. Wiktionary's translingual entry for œ (opens in a new tab) gives the same IPA value.

The IPA symbol and the oe letter French writes only partly overlap. The OQLF explains [œ] with the eu of neuf and [ø] with the eu of eux. Both sounds are spelled eu there. So a dictionary transcription with [œ] does not mean the word is written with œ. And a word written with œ, like fœtus, may contain no [œ] at all.

The ø in the table is the IPA symbol. For ø as a Danish and Norwegian letter, see the o with slash page. For German ö, see the o with umlaut page.

Which English words were once spelled with œ?

English used the oe symbol in borrowed Greek and Latin words. Wiktionary labels those œ spellings dated or archaic today. In British and other Commonwealth spelling the two letters now stand apart as oe. American spelling often keeps only the e.

Older spelling	Greek or Latin source	Commonwealth today	US today	How English says it
œsophagus	Greek οἰσοφάγος	oesophagus	esophagus	/iːˈsɒfəɡəs/ UK, /ɪˈsɑfəɡəs/ US
amœba	Greek ἀμοιβή, change	amoeba	ameba or amoeba	/əˈmiːbə/
phœnix	Latin phoenīx, from Greek φοῖνιξ	phoenix	phoenix	/ˈfiːnɪks/
Œdipus	Latin Oedipus, from Greek Οἰδίπους	Oedipus	Oedipus	/ˈɛdɪpəs/, /ˈiːdɪpəs/
fœtus	Latin fētus	foetus	fetus	/ˈfiːtəs/

The rows come from Wiktionary's entries for oesophagus (opens in a new tab), esophagus (opens in a new tab), amoeba (opens in a new tab), phoenix (opens in a new tab), Oedipus and fetus (opens in a new tab). In every transcription above, the oe is an ee, an i or an e sound. None of them is the rounded eu of French.

Here the American form is the older one. Wiktionary's foetus (opens in a new tab) entry quotes British medical writers of the 1960s. They argued that fetus matches the Latin and foetus was an old error. Today fetus is the main spelling in the United States, Canada, Australia and the sciences, while foetus stays common in the United Kingdom.

Why did œ go missing from computer text?

The oe symbol was hard to type long before computers. The OQLF notes that typewriters could not produce the double letters and word processors can. It adds a second problem. Latin alphabet No. 1, the ISO character set that the OQLF still calls the Internet's default, has room for æ and none for œ.

The Unicode Consortium's mapping tables show where œ ended up instead. Each code page put it at a different byte, so a file read with the wrong one shows a different wrong character. We decoded the word cœur with each byte layout on 2026-10-09, using Python 3.14, to fill in the last column.

Character set	Byte for œ, then Œ	cœur opened as Windows-1252
ISO 8859-1, Latin-1	none	nothing to open: the encoder refused to save œ
ISO 8859-15, Latin-9	BD, BC	c½ur
Windows-1252	9C, 8C	cœur, correct
Mac OS Roman	CF, CE	cÏur
UTF-8	C5 93, C5 92	cœur

The bytes come from the mapping files for ISO 8859-1 (opens in a new tab), ISO 8859-15 (opens in a new tab), Windows-1252 (opens in a new tab) and Mac OS Roman (opens in a new tab). Latin-9 put œ and Œ on the bytes where Latin-1 keeps the fractions ½ and ¼. That is why an old French page can show c½ur.

The Windows-1252 row also shows how to type œ with an Alt code. Alt+0156 types the byte 9C, which is 156 in decimal, and Alt+0140 types 8C.

The keyboard caught up last. The French standard NF Z71-300 was proposed by the culture ministry's language delegation. Its designers at norme-azerty.fr (opens in a new tab) say the new layout holds every character needed to write French, and they name œ as an example.

Will a search for coeur find cœur?

Only if the search folds the oe symbol on purpose. UnicodeData.txt gives œ no decomposition, so accent stripping leaves it alone. We ran each method on 2026-10-09 in Node.js v26.0.0, which uses ICU 78.3 and CLDR 48 data. The control pair café and cafe shows what each method does with a real accent.

Method	Does coeur match cœur?	Does cafe match café?
exact comparison	no	no
both sides lowercased	no	no
NFKD normalization, then marks removed	no	yes
ICU collator, French, base strength	yes	yes
ICU collator, French, accent strength	no	no

So a search box built on accent stripping finds café and still misses cœur. Only the loosest collation level joins the two spellings. If your search must match both, map œ to oe and Œ to OE yourself before you index the text.