Consider these masculine nominative singular and masculine nominative dual forms:

νοῦς, νώ
κανοῦν, κανώ
μνᾶ, μνᾶ
γῆ, γᾶ

I understand that the circumflex in these forms represents an acute accent that used be on the penult before a contraction occurred. For examples:

νόος → νοῦς
μνάᾱ → μνᾶ

νώ represents an exception because there is no circumflex to hint at what used to be an acute. Instead, we get:

νόω → νώ

On this, Introduction to Attic Greek 2nd ed. by Mastronarde Unit 40 says:

. . . the nominative, accusative, and vocative dual of uncompounded words has an acute (e.g. νώ instead of νῶ from νόω).

Also, some adjectives seem to follow the exceptional pattern. For example:

ἀργυροῦς (ἀργυρέος), ἀργυρώ (ἀργυρέω)
ἁπλοῦς (ἁπλόος), ἁπλώ (ἁπλόω)

QUESTIONS

1. Is there a way to understand the exception above? Maybe it is an instance of a large pattern, or there are some parallels to it. Otherwise, I would be happy to accept an exception as such.

2. The uncontracted form of κανοῦν is said to be κάνεον. By contraction I should have excepted κάνουν (which Perseus indeed lists as 'noun sg neut nom attic epic doric contr'). How does an accute on antepenult travel all the way to ultima by contraction? (If anyone thinks this second question should be a separate post I will be happy to make it so.)

Consider these masculine nominative singular and masculine nominative dual forms:

νοῦς, νώ
κανοῦν, κανώ
μνᾶ, μνᾶ
γῆ, γᾶ

I understand that the circumflex in these forms represents an acute accent that used be on the penult before a contraction occurred. For examples:

νόος → νοῦς
μνάᾱ → μνᾶ

νώ represents an exception because there is no circumflex to hint at what used to be an acute. Instead, we get:

νόω → νώ

On this, Introduction to Attic Greek 2nd ed. by Mastronarde Unit 40 says:

. . . the nominative, accusative, and vocative dual of uncompounded words has an acute (e.g. νώ instead of νῶ from νόω).

Also, some adjectives seem to follow the exceptional pattern. For example:

ἀργυροῦς (ἀργυρέος), ἀργυρώ (ἀργυρέω)
ἁπλοῦς (ἁπλόος), ἁπλώ (ἁπλόω)

QUESTIONS

1. Is there a way to understand the exception above? Maybe it is an instance of a larger pattern, or there are some parallels to it. Otherwise, I would be happy to accept an exception as such.

2. The uncontracted form of κανοῦν is said to be κάνεον. By contraction I should have excepted κάνουν (which Perseus indeed lists as 'noun sg neut nom attic epic doric contr'). How does an accute on antepenult travel all the way to ultima by contraction? (If anyone thinks this second question should be a separate post I will be happy to make it so.)