الخطة كانت جنون.

Because الخطة (the plan) is a feminine singular noun in Arabic, so the past-tense form of to be must agree with it.

• كان = he was / it was for masculine
• كانت = she was / it was for feminine

Even though plan is not biologically female, Arabic nouns have grammatical gender, and خطة is feminine.

So:

• الخطة كانت جنون = The plan was crazy / The plan was madness

In Arabic, many nouns ending in ـة (called taa marbuuTa) are feminine, and خطة is one of them.

So:

• خطة = plan
• الخطة = the plan

Because it is feminine, any verb or adjective connected to it often shows feminine agreement, like كانت.

In Arabic, the verb to be is usually not expressed in the present tense, but it is expressed in the past and future.

So compare:

• الخطة جنون = The plan is crazy / The plan is madness
• الخطة كانت جنون = The plan was crazy / The plan was madness

That is why كانت appears here: the sentence is in the past.

Literally, جنون means madness, insanity, or craziness.

In colloquial speech, especially in Levantine, it can also be used very naturally to mean:

• crazy
• insane
• wild
• unbelievable

So الخطة كانت جنون is literally something like:

• The plan was madness

but in natural English it often means:

• The plan was crazy
• That plan was insane

That is a very common feature in spoken Arabic. A noun can be used as the predicate to give a strong descriptive meaning.

So instead of saying:

• الخطة كانت مجنونة = The plan was crazy

a speaker may say:

• الخطة كانت جنون = The plan was madness / insanely crazy

Using جنون gives a more emphatic, expressive feel. It sounds a bit like saying in English:

• The plan was madness
• That plan was pure insanity

So this is not just grammar—it also adds style and intensity.

Yes, absolutely.

Both are possible, but they feel a little different:

• الخطة كانت مجنونة = The plan was crazy
  
  • more straightforward adjective use
• الخطة كانت جنون = The plan was madness / insanely crazy
  
  • more vivid, dramatic, colloquial

So جنون often feels stronger or more expressive.

Because جنون here is a noun, not a regular adjective.

If you use an adjective, it normally agrees in gender:

• الخطة كانت مجنونة
  feminine noun + feminine adjective

But in:

• الخطة كانت جنون

the word جنون stays the same, because it is being used as a noun meaning madness or craziness.

So there is no feminine ending needed here.

The structure is especially natural in spoken Arabic, including Levantine.

In Modern Standard Arabic, you are more likely to see something like:

• كانت الخطة مجنونة
• كانت الخطة ضربًا من الجنون = The plan was a kind of madness

The sentence الخطة كانت جنون sounds more colloquial, more like everyday speech.

Also, the word order with the subject first (الخطة) is very natural in Levantine.

In Levantine and other spoken varieties, subject-first word order is very common.

So:

• الخطة كانت جنون

is a very natural spoken pattern:
the plan + was + madness

You could also say:

• كانت الخطة جنون

and that sounds a bit more formal or more like Standard Arabic style.

So the version you have is very normal for conversation.

It is usually pronounced something like il-khiTTa or el-khiTTa in Levantine, depending on the region.

A few helpful points:

• ال is often pronounced il- or el- in Levantine
• خ is like a throaty kh sound
• ط is an emphatic t
• the final ـة is pronounced -a in pause: khiTTa

So a rough pronunciation is:

• il-khiTTa kaanet jnuun

In Levantine, كانت is commonly pronounced kaanet.

So the sentence sounds roughly like:

• il-khiTTa kaanet jnuun

A learner might expect something closer to formal pronunciation, but in everyday speech kaanet is very common.

They are related, but not the same part of speech:

• جنون = madness / insanity / craziness
  
  • a noun
• مجنون = crazy / insane for masculine
  
  • an adjective
• مجنونة = crazy / insane for feminine
  
  • an adjective

So:

• الخطة كانت جنون = The plan was madness / crazy
• الخطة كانت مجنونة = The plan was crazy

Both can describe the plan, but the noun جنون often sounds stronger or more colorful.

It can definitely be positive or negative, depending on context and tone.

In Levantine speech, words like جنون can be used very expressively. So:

• negative: The plan was insane in a bad way
• positive: The plan was unbelievably good / wild / amazing

This is similar to English, where crazy or insane can be either criticism or praise depending on context.

So you need the surrounding situation and the speaker’s tone to know the exact feeling.