Der Plan klingt merkwürdig.

Because der Plan is the subject of the sentence, so it is in the nominative case.

• der = nominative masculine singular
• den = accusative masculine singular
• dem = dative masculine singular

The noun Plan is masculine, so its basic dictionary form is der Plan.

In this sentence, the plan is the thing doing the sounding, so nominative is required:

• Der Plan klingt merkwürdig. = The plan sounds strange.

German main clauses usually follow the verb-second rule (V2). That means the finite verb comes in the second position.

Here:

• Der Plan = first element
• klingt = finite verb in second position
• merkwürdig = the rest

So the structure is:

Der Plan | klingt | merkwürdig.

This is one of the most important basic word-order patterns in German.

klingt is the 3rd person singular present tense form of klingen.

Conjugation in the present:

• ich klinge
• du klingst
• er/sie/es klingt
• wir klingen
• ihr klingt
• sie/Sie klingen

Since der Plan is a singular noun, German uses the same verb form as er:

• der Plan klingt

Here klingen means to sound.

So Der Plan klingt merkwürdig literally means:

• The plan sounds strange.

German often uses klingen the same way English uses sound:

• Das klingt gut. = That sounds good.
• Das klingt interessant. = That sounds interesting.

It does not mean that the plan is making an actual noise. It means it seems strange based on how it is described.

Because merkwürdig is being used as a predicate adjective after the verb klingt.

In German:

• Adjectives before a noun usually take endings:
  • ein merkwürdiger Plan
• Adjectives after verbs like sein, werden, bleiben, klingen do not take endings:
  • Der Plan ist merkwürdig.
  • Der Plan klingt merkwürdig.

So here, merkwürdig stays in its base form.

There is a small but important difference:

• Der Plan ist merkwürdig.
  = The plan is strange.
  This sounds more direct and definite.

• Der Plan klingt merkwürdig.
  = The plan sounds strange.
  This is softer and means based on what I hear, it seems strange.

So klingt expresses an impression, not necessarily a final judgment.

Merkwürdig usually means:

• strange
• odd
• peculiar
• sometimes weird

Depending on context, it can be mild or fairly strong.

Examples:

• Das ist merkwürdig. = That is strange.
• Ein merkwürdiger Zufall. = A strange coincidence.

It is often a good neutral translation for strange or odd.

Because all nouns are capitalized in German.

So:

• der Plan
• das Haus
• die Idee

This is a standard rule, not something special about this sentence.

A rough English guide would be something like klingkt, but smoothly.

A few points:

• kl- sounds like English cl- in clean
• -ing- is similar to sing, but shorter
• the final -t is clearly pronounced
• the g is not silent; it combines with the following t in the cluster

So try something like:

klingt → klingkt

Just remember that it is one compact syllable.

Yes, you can. German allows different elements to come first, as long as the finite verb stays in second position.

So these are both possible:

• Der Plan klingt merkwürdig.
• Merkwürdig klingt der Plan.

The second version sounds more marked or stylistic because it emphasizes merkwürdig.

For a learner, Der Plan klingt merkwürdig is the most neutral and natural basic order.