Recently, the discussion around my supper table
turned to the fact that, in English, with the word "old",
one generally uses cardinal numbers; that is:
one says:  "He is ten years old" and not
* "He is tenth year old". (Living in a bilingual houshold
results in some very interesting suppertimes!  ;-)   )
It _is_ possible to use ordinal numbers, as in
"He is in his tenth year", but it's not usually done
(at least in the variety of English that I speak).

This got me wondering how we all refer to
age in our various conlangs. In my conlang, rtemmu,
I use ordinal numbers to refer to age. For example:

"He/She is 40 years old"   would be:

( o` = [O];  g~ = [N] )

inawasyasna duhl auag nu tukuhyehvdo`g~leh na dwexas.

or, broken down into component parts:

i-na-wasyas-na duhl auag nu tukuh-yeh-vdo`g~l-eh na dwe-xas.

i = the speaker observes (objectively or subjectively)
na = the speaker is developing, subjectively, at a normal rate
wasyas = new instance of a repeating process
[ Notice that the "wasyas" refers to the repetition of the
person-process, not the year!]
na = the 3rd person singular process (ie "he" or "she",
"it" etc.) is developing, subjectively, (so the speaker assumes)
at a normal rate
duhl = 3rd person singular process
auag = conjunction signifying assertion
nu = the speaker's concept of the following number is
developing to slow for him/her to notice
tukuh = 10
yeh  = multiplied by
vdo`g~ = 4
leh = changes a cardinal number into an ordinal number
na = the year is subjectively changing at a normal rate
dwe = year
xas = during

Or, loosely, "He/She is enduring for the 40th time a year".

This is more or less a neutral way of saying it.
If I wanted to be nasty,  ;-)  I would substitute an objective
rate-of-change marker for the subjective which refers to
the 3rd person singular process:

i-na-wasyas-KEHS duhl auag nu tukuh-yeh-vdo`g~l-eh na dwe-xas.

Since kehs refers to objectively observed normal rate of change,
depending upon context, it might mean: "He/She is only 25, but
looks (like hell ;-) ) like a 40 year old. Or  "(Isn't he/she wonderfully
preserved!)  He/She is really 70, but (thanks to surgery?) looks like
a 40 year old!"   ;-)

One could get really nasty in rtemmu by changing the rate-of-change
marker to an objectively faster rate, say "fis" as in

i-na-wasyas-FIS duhl auag nu tukuh-yeh-vdo`g~l-eh na dwe-xas.

It still means "He/She looks to be 40 years old" but this time the
nuances are: That young person is going to hell in a handbasket!
(Too much fast living!) or That old person is getting younger-looking
every day (It's simply amazing what surgery can do these days!).

If I _really_ wanted to be nasty, I could always add  "ut", the
acceleration marker to "kehs" or "fis". ;-)

Anyhow, that's how I handle age in rtemmu. How do you all do