父さん|とうさんtousan[1]atamadaka (head-high)

1. nounfather; dad; papa; pa; pop; daddy; dada
   彼かれは父とうさんほど背せが高たかくない。↗

   He is not as tall as his father.

• Synonymお父さんおとうさんNeutralThe most common way to address your father, warm but respectful; 「父さん」 simply drops 「お」, making it more casual.
• Synonym父ちちNeutralA humble term for your own father when talking to outsiders, in speech or writing, as in 「父は会社員です」; never used to address him directly.
• Synonym父親ちちおやNeutralA neutral, objective word for father, also common in everyday speech, as in 「うちの父親」; not used when addressing him directly.
• SynonymおやじCasualColloquial, mainly used by men for their own father, with a rough, macho feel; also means a middle-aged man or one's boss.
• Synonymお父様おとうさまFormalA formal, respectful term for father that can refer to your own or someone else's; 「父さん」 is far more casual and intimate.
• Synonym父上ちちうえFormalAn old-fashioned honorific for father, heard mostly in period dramas or traditional families; almost never used in daily life today.
• Synonym父君ふくんWrittenA written, archaic honorific for father, now very rare; in everyday speech say 「お父さん」 instead.
• SynonymファーザーNeutralA loanword; almost never used to address one's own father in daily life, say 「父さん」 or 「お父さん」 instead.
• Related男親おとこおやWrittenA written-style word contrasted with 「女親」 that stresses the father's side of parenting; descriptive, not a form of address.
• Related父御ちちごWrittenAn archaic honorific used only for someone else's father; rarely heard in modern Japanese.
• RelatedおとっつぁんCasualAn Edo-style colloquial way to say dad, now mostly heard in period dramas; rustier and more old-fashioned than 「父さん」.
• Antonym母さんかあさんCasualA casual way to say mother, less formal than 「お母さん」; the female counterpart of 「父さん」.

To address your father, 「お父さん」 is the default and 「父さん」 is more casual; men often say 「親父」. When mentioning your own father to outsiders, say 「父」; 「お父様」 is the respectful term, used above all for someone else's father. 「母さん」 is for mother.

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

1. 自分じぶんの父親ちちおや。「おとうさん」よりもくだけた表現ひょうげん。