定か|さだかsadaka[1]atamadaka (head-high)

1. na-adjective, noundefinite; sure
   船田ふなだ氏しが新党しんとうに加くわわるかどうかは、定さだかでは、ない。↗

   It is not certain if Mr Funada will join the new party.

• Synonym明確めいかくNeutralNeutral. Clear and unambiguous, with no room for doubt, as in 「明確な目標」; it stresses clarity of expression, unlike 「定か」, which usually appears in negatives.
• Synonym明らかあきらかNeutralNeutral. Says something is obvious or plainly evident, as in 「明らかな誤り」; common in both speech and writing.
• Synonym確実かくじつNeutralNeutral. Emphasizes reliability and freedom from error, as in 「確実な方法」 or 「確実な情報」; use it for trustworthy certainty rather than clarity.
• Synonym明瞭めいりょうWrittenWritten/formal prose. Means clear to the ear or eye, as in 「発音が明瞭」; a formal word for perceptible clarity, not for settled facts.
• Synonym確かたしかNeutralNeutral. Means certain and reliable; as an adverb it hedges a memory ('if I remember right'). Common in speech.
• Related明晰めいせきWrittenWritten/formal prose. Describes clear thinking or lucid argument, as in 「明晰な頭脳」; a formal word found mainly in writing.
• Related明快めいかいNeutralNeutral. Describes explanations or answers that are crisp and well-organized, as in 「明快な答え」; it stresses being clean-cut rather than certain.
• Related鮮明せんめいNeutralNeutral. Describes vivid images or clear-cut positions, as in 「旗幟鮮明」; it stresses being striking and unmistakable, not certainty.
• Related正確せいかくNeutralNeutral. Means accurate and free of mistakes, matching the facts, as in 「正確な時間」; use it for precision, not for whether something is settled.
• Related決定的けっていてきNeutralNeutral. Means decisive or final, as in 「決定的瞬間」; it stresses something that determines the outcome, a different sense from 「定か」.
• Related自明じめいWrittenWritten/formal prose. A noun meaning self-evident, needing no proof, as in 「自明の理」; formal and mostly seen in writing.
• RelatedクリアNeutralNeutral loanword. Means clear or transparent, and also clearing, passing or solving something; common in speech and broader in use than 「定か」.
• Related確定的かくていてきWrittenWritten/formal prose. Says something is already settled and will not change, as in 「当選が確定的」; formal, while 「定か」 usually appears in negatives.
• Antonym曖昧あいまいNeutralNeutral antonym. Means vague or ambiguous, the opposite of the clear and definite 「定か」.
• Antonym不確かふたしかNeutralNeutral antonym. Means uncertain or unreliable, the direct opposite of 「定か」, as in 「記憶が不確か」.

「定か」 mostly appears in negatives like 「定かではない」, saying something is unclear or a memory is uncertain. For plain certainty say 「確か」, for the obvious 「明らか」, for clear statements 「明確」, for accuracy 「正確」. Other near-synonyms narrow the sense: 「確実」 reliable, 「鮮明」 vivid, 「明晰」 and 「明瞭」 formal clarity. When something is vague, use 「曖昧」 or 「不確か」.

Usage comparisons are AI-assisted and cross-checked by multiple models; for study reference only

1. 物事ものごとがはっきりとして確実かくじつである様子ようす。不動ふどうである様子ようす。