Correct spelling, explanation: the word detailed is the adjective form of the noun detail and follows a common English pattern where a verb is turned into an adjective using the -ed suffix. The verb detail ends in a single -l, and when forming the adjective, we simply add -ed without doubling the consonant. Some words do have different spellings in American vs. British English (e.g., travelled vs. traveled), but detailed is the correct spelling in both. There is no variation where detailled would be correct.

Definition of detailed:
Adjective, having many details or facts; showing attention to detail
She provided a detailed explanation of the project, ensuring that everyone understood each step.
The detective carefully examined the detailed notes left at the crime scene.

Collocations with detailed:
Some of the most commonly used collocations include:
1. Detailed analysis: a thorough and in-depth examination of something.
The scientist conducted a detailed analysis of the test results before drawing conclusions.
2. Detailed explanation: a clear and comprehensive description of something.
The teacher gave a detailed explanation of the math problem to help students understand it.
3. Detailed description: a thorough account of something, often including small details.
The witness provided a detailed description of the suspect to the police.
4. Detailed report: a document or account that includes all relevant details.
The manager requested a detailed report on last month’s sales performance.

Incorrect spelling, explanation: the word detailled is a mistake because it does not follow standard English spelling rules. The adjective detailed comes from the verb to detail, meaning to describe something thoroughly. When we form the past tense or an adjective from this verb, we add -ed. Since detail has a long vowel sound and is stressed on the first syllable (DE-tail), it does not follow the doubling rule.