also: デイ · ディ
Suffix attached to nouns to form names of special days, observances, or holidays. Often used in commercial or promotional contexts.
来月のバレンタインデーに何をあげる？
What will you give on Valentine's Day next month?
This supermarket has a 'five-times-points day' on the 5th of every month.
At this store, every Friday is double points day.
noun-modifying (irregular)
Prenominal element used in compounds to indicate something occurring during the day, as opposed to night. Most commonly seen in デーゲーム (day game).
See also: デーゲーム
今日の試合はデーゲームだから、暑さ対策を忘れずに。
Today's match is a day game, so don't forget to prepare for the heat.
Most common spelling; used in many established compounds.
Alternate spelling, also common; often seen in loanwords.
Irregular kana usage; less common and may be considered non-standard.
Borrowed from English 'day'. The spelling デー reflects a long vowel adaptation, while デイ preserves the original diphthong. ディ is an irregular variant.