This is the 617th most frequent French word.
lendemain
The day after.
Here, 'lendemain' refers to 'the day after a specific point in time', functioning as a noun to indicate temporal succession.
Nous partirons le lendemain.
We will leave the next day.
In this sentence, 'lendemain' is used with a complement to specify 'the day after' a particular event (his arrival). It's employed as a marker in a temporal expression.
Le lendemain de son arrivée, il a visité la ville.
The day after his arrival, he visited the city.
Here, 'lendemain' again signifies 'the day following a reference day', and serves as a concrete reference to time.