yosasou 良さそう

In Japanese, yosasou よさそう, also spelled yosasou 良さそう, means "looks like it's good." It's what you get when you add the sou そう suffix to the sa-form of the i-adjective yoi よい, "good." It's also de facto the sou-form of the synonym ii いい.

• 良さそうな
• 良そう vs. 良さそう

Yosasou-na 良さそうな

The phrase yosasou-na 良さそうな is yosasou treated as a na-adjective by adding the na な copula to it.

• ii hito
  いい人
  Good person.
• yosasou-na hito
  良さそうな人
  Person [that] looks like [he's] good.
  [Someone who] looks like a good person.

• atama ga ii
  頭がいい
  "Head is good."
  Smart.
• atama ga yosasou na hito
  頭が良さそうな人
  Person [whose] head seems good.
  A person [that] seems smart.

• naka ga ii 仲がいい
  "Relationship is good."
  In good terms. Friends.
• naka ga yosasou na kappuru
  仲が良さそうなカップル
  A couple [whose] relationship seems good.
  A couple [that] seems in good terms.

This works because sou is a na-adjective, so any word that has the sou suffix is a na-adjective.

Since yosasou is a na-adjective, it can be conjugated to adverbial form, etc. like one:

• mieru
  見える
  To be able to see.
  To be seen. To appear [in a way]. To be visible. (because someone can see it.)
• yoku mieru
  よく見える
  To see well. (it's very visible.)
  [I can] see [that] well.
  • yoku is the adverbial form of the i-adjective yoi よい.
• yosasou-ni mieru
  良さそうに見える
  To look like it's good. (you actually saw it, and it "looked good," yosasou.)
  • yosasou-ni is the adverbial form of the na-adjective yosasou.

Yosou vs. Yosasou

One important thing to note about yosasou is that when adding the sou そう suffix to normal adjectives to say "looks like..." You normally add it to their stem, for example:

• warui
  悪い
  Bad.
• warusou
  悪そう
  Looks bad.
• warusou-na hito
  悪そうな人
  A person [that] looks like [he's] bad.

But because Japanese hates you, yosasou よさそう gets the sou suffix added to its sa-form, yosa よさ, instead of the stem.

• kimochi-ii
  気持ちいい
  Good-feeling.
  Pleasant.
• kimochi-yoi
  気持ちよい
  (same meaning.)
• kimochi-yo-sa
  気持ちよさ
  Good-feeling-ness.
  How good it feels.
• kimochi-yo-sa-sou
  気持ちよさそう
  To look like it feels good.
• kimochi-yo-sa-sou-na kao
  気持ちよさそうな顔
  A face [that] looks like [it] feels good.
  [He] looks like [he's enjoying himself.] (e.g. his facial expression tells he's enjoying an activity, like singing, watching the clouds, going on a psychopathic murderous rampage, sleeping, dancing, etc.)

This isn't normal: the only other adjective that gets sou そう added to the sa-form instead of the stem is nai 無い. Probably all other i-adjectives get sou added to the stem. It's just yosasou and nasasou that are weird.

• kane ga nai
  金がない
  Money is nonexistent.
  There's no money. To have no money.
• kane ga nasasou-na hito
  金が無さそうな人
  A person [that] looks like [he] has no money.