As t-samhradh or The mysterious t-

Who hasn't wondered about why the seasons behave very strangely in Gaelic? And I'm not talking about the incessant rain.

The words for the seasons are straightforward enough, but when it comes to saying "in the X" they seem to violate everything you have learned about prepositions:

anns an ogha	in the grandson	as t-earrach	in (the) spring
anns an t-saor	in the joiner	as t-samhradh	in (the) summer
anns an fhlaith	in the nobleman	as t-foghar	in (the) autumn
anns a' ghleann	in the valley	sa gheamhradh	in (the) winter

Summer and Winter are what you would expect them to be, but what about Spring and Autumn? What we have here are actually two frozen forms - two expressions which at one point became so established in the language that they never changed, even when the rest of the language had moved on. It's like the Queen signing bills with La Reine le veult [la rɛinə lə veylt] in Norman French even though in modern French this phrase is La Reine le veut [la ʁɛn lə vø]). No one in Britain speaks Norman French any more yet the phrase has survived the changes of linguistic fortune.

Just accept from me that some things in the Old Irish case system worked differently. The dative case was one of those things. In Old Irish, these expressions with the seasons were formed quite regularly, as shown below. Examples of today's seasonal expressions, with their translations, are shown above:

is ind áuu (ogha)	[isin taː.u]	is ind erruch (earrach)	[isin derːux]
is int ṡóer (saor)	[isin toeɾ]	is int sámrad (samhradh)	[isin taːvrað]
is int ḟlaith (flaith)	[isin tɫ̪aiθ]	is int fogmar (foghar)	[isin toɣvaɾ]
is in glinn (gleann)	[isi ʝlinː]	is in gaimred (geamhradh)	[isin ɣaivɾʲeð]

(Note the IPA above is full IPA)

As you can see, in the dative case, Old Irish regularly used in, English "in". It used ind as the definite article before vowels, int as the definite article that lenited s and f, and for all other instances it used in (is in chatt (cat); is in bard (bàrd) etc.).

At some point, the system changed (you don't want to know, you really don't) and we were left with the modern system which does what we all do: nothing before a vowel (anns an ogha); retain t- before s (anns an t-saor); lenite f (anns an fhlaith); and lenite elsewhere (unless lenition is blocked) (anns a' ghleann). But during the time the old dative system was being eliminated, the phrases in spring/in summer/in autumn/in winter were so entrenched that they didn't undergo the same changes.

Modern Irish has fully innovated this system, by the way:

san earrach

sa samhradh

san fhómhar

sa gheimreadh

So, as t-earrach is 100% correct in modern Gaelic, even though it reflects something that was common a long time ago. Isn't language wonderful? Enjoy your summer!