This is the 30th most frequent Latvian word.
ja
"If."
In this sentence, 'ja' is used as a subordinating conjunction meaning 'if', used to introduce a conditional clause.
Ja rīt būs silts, mēs iesim uz pludmali.
If it is warm tomorrow, we will go to the beach.
Here, 'ja' is used as a direct translation of 'if', introducing a reported yes/no question.
Es viņam jautāju, ja viņš vēlas pievienoties vakariņām.
I asked him if he would like to join for dinner.
In this example, 'ja' is used again as 'if', combined with 'nu' to add a hypothesis or doubt aspect.