Learn Hardcore Greek: Επίσης, έχει την ίδια ιδέα με εσένα.

Επίσης means "also / in addition." The comma after an introductory Επίσης is optional style: both Επίσης, έχει… and Επίσης έχει… are fine.

Can I put Επίσης somewhere else in the sentence?

Yes. Common options:

Έχει επίσης την ίδια ιδέα με εσένα. (neutral)
Αυτός/Αυτή επίσης έχει την ίδια ιδέα με εσένα. (after the expressed subject)
Έχει την ίδια ιδέα με εσένα επίσης. (end position; sounds like an add-on “too”)

All are grammatical; initial position is the most typical.

Who is the subject of έχει here?

Greek is a "null-subject" language, so the subject pronoun is usually omitted. Έχει is 3rd person singular, so it could mean "he/she/it has." If you need to make it explicit, add a subject: Αυτός/Αυτή έχει… or a name.

Why use έχει (“has”) and not είναι (“is”)? Could I say “agrees with you”?

Greek naturally says έχει την ίδια ιδέα ("has the same idea"), not είναι την ίδια ιδέα. To express agreement, you can also say:

Συμφωνεί μαζί σου. (He/She agrees with you.)
Έχει την ίδια άποψη/γνώμη με εσένα. (He/She has the same opinion as you.)

Why is it εσένα and not εσύ?

Because με ("with") is a preposition that requires the accusative case. Εσύ is nominative (subject form); εσένα (or σένα) is the accusative (object) form, which is required after με: με εσένα / με σένα.

What’s the difference between με εσένα, με σένα, and μαζί σου?

με εσένα: full/neutral; can add emphasis.
με σένα: shorter, very common in speech; same meaning.
μαζί σου: literally “together with you.” It’s perfect with verbs like συμφωνώ (e.g., Συμφωνεί μαζί σου), but with έχει την ίδια ιδέα we typically prefer με εσένα/σένα, not μαζί σου.

When do I use εσάς instead of εσένα?

Use εσάς for plural "you" or for polite/formal singular:

…με εσάς = with you (plural/formal).
Informal singular remains …με εσένα/σένα. (After prepositions, prefer the strong forms εσένα/εσάς over the weak σας.)

Why is it την ίδια ιδέα? What’s the role of the article την?

With ίδιος/ίδια/ίδιο meaning "the same," Greek normally uses the definite article:

την ίδια ιδέα = "the same idea." Without the article, ίδια ιδέα sounds unusual here or more like "identical idea" in a technical/attributive sense. The article is the normal, idiomatic choice.

Why is it ίδια and not ίδιο or ίδιος?

Agreement. Ιδέα is feminine singular, so everything matches:

Article: την (feminine accusative singular)
Adjective: ίδια (feminine accusative singular)
Noun: ιδέα (feminine singular) Other forms: ο ίδιος (masc), η ίδια (fem), το ίδιο (neut).

Can I say Έχει το ίδιο με εσένα instead of την ίδια ιδέα?

Only if the noun is clear from context: το ίδιο can stand in for "the same (thing)" when it’s understood (e.g., after you've just mentioned σχέδιο "plan"). In isolation, Έχει το ίδιο με εσένα sounds incomplete; with "idea," keep την ίδια ιδέα.

How do I pronounce key words here?

Επίσης: [eˈpisis] (e-PEE-sees)
έχει: [ˈeçi] (EH-khi; χ like German “ich”)
ίδια: [ˈiðja] (EE-thya; δ like voiced “th” in “this”)
ιδέα: [iˈðea] (ee-THE-a; δ voiced “th”)
εσένα: [eˈsena] (e-SE-na)

Is Επίσης the only way to say “also”?

No. Alternatives:

Και: often placed before the element being added, e.g., Κι αυτός έχει… ("He also has…").
Ακόμα/Ακόμη: "also/furthermore" (can also mean “still,” so watch context).
Επιπλέον: "furthermore," more formal.

Can I use other nouns instead of ιδέα, like “opinion”?

Yes, very natural:

…έχει την ίδια άποψη με εσένα.
…έχει την ίδια γνώμη με εσένα. These often fit better when you mean agreement of viewpoints.

Can I change the word order for emphasis?

Greek allows flexible order:

Κι αυτός/Αυτή έχει την ίδια ιδέα με εσένα. (emphasizes the subject "he/she too")
Την ίδια ιδέα με εσένα έχει κι αυτός/αυτή. (fronts the shared idea for emphasis) All remain grammatical.

How would I make it plural (“They also have the same idea as you”)?

Change the verb and any pronouns:

Επίσης, έχουν την ίδια ιδέα με εσένα. For formal/plural "you": …με εσάς.