1Soon; before long — indicates something will happen in the near future.
やがて桜が咲き、町はピンクに染まった。
Before long the cherry blossoms bloomed and the town was dyed pink.
雨はやがて止むでしょう。傘を畳んでいいですよ。
The rain should stop soon. You can fold your umbrella.
彼はやがてその真意に気づくだろう。
He will soon realize the true meaning.
2Used mainly in formal/written Japanese with numbers or durations to mean nearly or almost reaching that amount.
犠牲者の数はやがて100人に達するとみられている。
The number of victims is expected to reach nearly 100.
工事が始まってから、やがて3年になる。
It has been almost three years since construction began.
3Eventually; in the end — indicates that after some time or process, a certain result is reached.
彼らはやがて和解し、友人に戻った。
They eventually reconciled and returned to being friends.
やがて夜が明け、新しい一日が始まった。
At last dawn broke and a new day began.
長年の努力はやがて実を結ぶだろう。
Years of effort will eventually pay off.