Four spellings are given for the same word. Choose the correctly spelt form of the English word that means sure or certain, that is, DEFINITE.

Introduction / Context:
Spelling questions test the learner understanding of common word patterns in English. Here, four variants of the word that means sure or clearly decided are given, and only one of them matches the standard dictionary spelling. Knowing how to spell definite is important because it is a very frequent word in academic writing and formal communication.

Given Data / Assumptions:

• Target word meaning sure or certain: definite.• Options: Definite, Diffinite, Defenite, Difinite.• Only one of these matches the correct spelling used in dictionaries and textbooks.• We assume standard British or international English.

Concept / Approach:
The word definite comes from the Latin root finis meaning limit or boundary. Over time, English has fixed the spelling as definite, with the sequence d e f i n i t e. There is only one f, and the vowel pattern is e i i e. Exam setters often introduce extra letters or swap vowels to create confusing but incorrect variants. The task is to recall or recognise that the correct spelling uses one f and has nite at the end, similar to finite.

Step-by-Step Solution:
Step 1: Recall familiar phrases such as definite answer, definite plan, or definite article, and visualise the spelling in those contexts.Step 2: Examine option A Definite. It has one f and ends with nite, which matches how the word is usually seen.Step 3: Consider option B Diffinite, which has double f and double f i at the beginning, a pattern that does not correspond to any known English form of the word.Step 4: Look at option C Defenite, where the e and i positions are swapped, producing an unfamiliar and incorrect pattern.Step 5: Check option D Difinite, where the first vowel is i instead of e, again creating a spelling that does not appear in standard use.Step 6: Conclude that Definite in option A is the correct spelling.

Verification / Alternative check:
One helpful comparison is with the word finite, which shares the same root and ends with nite. The positive forms definite and finite align in spelling in their final letters. Dictionaries and grammar books consistently use definite with the exact pattern seen in option A. The other options do not appear in authoritative sources and would be underlined as errors by any spell checker.

Why Other Options Are Wrong:
Diffinite incorrectly doubles the consonant f and introduces an unusual pattern of letters that is not supported by the word origin. Defenite alters the central vowels and breaks the connection with finite, which is a useful anchor. Difinite swaps the first vowel to i, making the whole word look unfamiliar and nonstandard. All three are typical distractors used in examinations to test spelling under pressure.

Common Pitfalls:
Many learners confuse definite with definition, where the sequence is d e f i n i t i o n. They sometimes try to copy that extra i into the shorter adjective or alter the vowels in the middle. A simple trick is to remember the pair finite and definite, both using f i n i t e at the end. Writing the word a few times and using it in your own sentences can also help fix the spelling firmly in memory.

Final Answer:
The correctly spelt form of the word is Definite.