長期間, ちょうきかん
Adverb, May take 'no'
long period (of time)
長期間の練習が彼が流暢な英語を話すことを可能にした。
に
Particle
1. at (place, time), in, on, during
2. to (direction, state), toward, into
3. for (purpose)
4. because of (reason), with
5. by, from
わたる, 渡る
Godan verb, Intransitive, occ. written as 渉る
1. to cross over, to go across
See にわたって, Usually in kana, occ. written as 亘る or 亙る
2. to extend, to cover, to range, to span
橋は安全です。車でわたれます。