This is the 132nd most frequent Finnish word.
ensimmäinen
"Ensimmäinen" means "first" in English.
Here, 'ensimmäinen' is used as an ordinal number to indicate the first instance of experiencing winter in Finland.
Ensimmäinen talvi Suomessa oli hyvin kylmä.
The first winter in Finland was very cold.
In this sentence, 'ensimmäinen' specifies the order of arrival among people.
Hän oli ensimmäinen henkilö, joka saapui juhliin.
He was the first person to arrive at the party.
The word 'ensimmäinen' here metaphorically refers to the initial phase of a process or journey.