What is the specific difference between old English and modern English?

The difference is too big. Where can we finish? Phonetic grammar vocabulary.

Phonetically:

The ancient word nama [nama] is now called [neim]

The ancient word fot [fot] is now foot[fut]

The ancient word hus [hus] is now house[haus]

Grammatically:

In the old saying, nouns are divided into yin and yang. For example, scip (modern ship) is neutral, and adjectives that modify it should also be neutral.

The deformation of ancient characters is far from perfect. Nouns other than pronouns are nominative, accusative, dative and possessive.

Stan masculine (now stone) singular nominative case

Complex nominative stanas

And the plural nominative case of scip is scipu.

In modern English, the plural is basically just S.

Today's verbs have only a few variants at most.

Write write write write.

And ancient verbs are much more complicated.

Lufei (now love)

Luffy Luffy Luffy

Lexically:

Too many real English words (old Germanic words) have been abandoned. Today, more than 80% of English vocabulary comes from French, indirectly or directly from Latin and Greek.