Breakdown of toraiarukikan wa mijikai.

Questions & Answers about toraiarukikan wa mijikai.
A natural reading is:
トライアルきかん は みじかい。
Romanized: toraiaru kikan wa mijikai
- トライアル = trial
- 期間 = period; duration
- は is written ha but pronounced wa here
- 短い = short
So the whole sentence is read Toraiaru kikan wa mijikai.
Because トライアル is a loanword, borrowed from English trial.
In Japanese:
- katakana is commonly used for foreign loanwords
- hiragana is used for native grammar words and some native words
- kanji is used for many core content words
So in this sentence:
- トライアル is katakana because it is a borrowed word
- 期間 and 短い are native Sino-Japanese / Japanese vocabulary, so they use kanji