Learn Hardcore German: Wenn dir etwas Besseres einfällt, sag mir bitte Bescheid. - If something better comes to your mind, please let me know.

Because the verb einfallen uses a dative experiencer: "etwas fällt jemandem ein." Here, dir is dative "to you." The subject is etwas Besseres ("something better"), so the verb agrees with that, not with "you." Compare: Mir fällt nichts ein. / Fällt dir noch was ein?

Why is the verb written as "einfällt" at the end instead of "fällt ... ein"?

Because wenn starts a subordinate clause, which sends the finite verb to the end. With separable verbs like einfallen, the prefix reattaches in subordinate clauses: wenn es mir einfällt. In a main clause you'd split it: Dir fällt etwas Besseres ein.

What does "etwas Besseres" mean, and why is "Besseres" capitalized and ending in -es?

Etwas Besseres = "something better." Besseres is a nominalized adjective (an adjective used as a noun), which is capitalized in German, especially after words like etwas, nichts, viel, wenig, alles. The -es ending is the strong ending for neuter nominative/accusative singular after no article. Similar: nichts Gutes, etwas Neues.

Who is the grammatical subject of the clause?

The subject is etwas Besseres. Dir is a dative complement required by einfallen. That's why the verb is third-person singular: einfällt.

What does "Bescheid" mean here, and why is there no article?

Bescheid is a noun ("notice/decision"), but in set phrases it forms an idiom meaning "to let someone know": Bescheid sagen/geben and Bescheid wissen. In these idioms it appears without an article: Sag mir Bescheid, Ich weiß Bescheid. It is always capitalized because it’s a noun.

Why "sag" and not "sage" or "sagst"?

Sag is the informal singular imperative of sagen. Sage is also correct but sounds formal or old-fashioned in everyday speech. Sagst is the present-tense 2nd person form, not an imperative. Formal imperative would be: Sagen Sie mir bitte Bescheid.

Can I say "Gib mir bitte Bescheid" instead of "Sag mir bitte Bescheid"?

Yes. Bescheid sagen and Bescheid geben are both standard and mean the same here. You can also say: Meld dich (bei mir), wenn dir ... einfällt, or more formal: Bitte informieren Sie mich, falls ....

Why does "dir" come before "etwas Besseres"? Could I say "Wenn etwas Besseres dir einfällt"?

German tends to place short pronouns before longer noun phrases. Since dir is a pronoun and etwas Besseres is an indefinite noun phrase introducing new information, Wenn dir etwas Besseres einfällt is the most natural order. Wenn etwas Besseres dir einfällt is possible but sounds marked.

Why not "Wenn du dir etwas Besseres einfällst"?

Because with einfallen the "thing" is the subject, not the person. It’s "etwas fällt dir ein," not "du fällst dir ein." If you want "you" as subject, you’d need a different verb, e.g., Wenn du an etwas Besseres denkst ....

Where can I put "bitte"? Is "Bitte sag mir Bescheid" okay?

Yes. Natural options include:

Sag mir bitte Bescheid.
Bitte sag mir Bescheid.
Sag mir Bescheid, bitte. (fine, a bit afterthought-like) Avoid Sag bitte mir Bescheid; placing the dative pronoun after bitte sounds awkward.

Do I need the comma? What if I flip the clause order?

Yes, subordinate clauses introduced by wenn are separated by a comma. You can also place the main clause first: Sag mir bitte Bescheid, wenn dir etwas Besseres einfällt. The meaning is the same.

Is there any difference between "wenn" and "falls" here?

Both can mean "if." Wenn is neutral and also means "whenever" in other contexts. Falls leans toward "in case" and can sound a bit more hypothetical or formal: Falls dir etwas Besseres einfällt, .... In everyday speech, wenn is more common.

Can I use "was" instead of "etwas"?

Colloquially, yes: Wenn dir was Besseres einfällt .... Was is the spoken, informal variant of etwas in many regions. In writing or formal contexts, prefer etwas.

Why "mir" and not "mich"? How does "sagen" handle objects?

With sagen, the person you tell is in the dative, and the thing you say is in the accusative: jemandem etwas sagen. Here, mir is dative ("to me"), and the "thing" is the idiomatic noun Bescheid: Sag mir (Dat.) Bescheid (Acc.). Not: sag mich.

How would I make this formal or plural?

Formal singular/plural: Wenn Ihnen etwas Besseres einfällt, sagen Sie mir bitte Bescheid.
Informal plural: Wenn euch etwas Besseres einfällt, sagt mir bitte Bescheid.

What tense/person is "einfällt" and why?

Present tense, third person singular, agreeing with the subject etwas Besseres (neuter singular). The dative dir does not control agreement.