#predicate-logic

Question

Why "Birds can't fly" and "Every bird can't fly" are not same?

Comments

“Every Bird Can’t Fly”, in simple English language, day-to-day language, would mean “Some Birds can’t fly”.

“Birds can’t fly” would mean “No bird can fly”.

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@Deepak Poonia

Doubt arise when translate predicate logic in to english sentence. 

like $\forall_x$[B(x) $\rightarrow\neg$F(x)]

it seems like "all birds can't fly" but it's wrong that's why I explain this. So, is my explanation correct? please confirm.... Thanks Sir

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The unambiguous way of reading the expression $\forall x[B(x) \rightarrow \neg F(x) ]$ is “No bird can fly”.

Answer 1

Comments

@ankitgupta.1729 @Deepak Poonia

is my answer correct??? 

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@pavan singh Your first order logic expressions given at the end are correct.

Answer 2

Birds can’t fly meaning all birds cannot fly.

Every bird can’t fly means there are some birds that cannot fly.

Comments

Even though you meant the same the first sentence should be

“Birds can’t fly means no bird can fly”