Using each letter only once, how many distinct meaningful English words (using common everyday vocabulary) can be formed from the letters E, S, R and O?

Introduction / Context:
This is a classic alphabet test question on word formation. You are given a small set of letters and asked how many meaningful English words can be made from them when each letter is used exactly once. Such questions check your vocabulary, your ability to permute letters, and your discipline in counting distinct words without repetition or overcounting.

Given Data / Assumptions:
• The given letters are E, S, R and O.
• Each letter can be used at most once in any word we form.
• We only count meaningful English words that are commonly used, such as basic nouns or adjectives that a general exam taker is expected to know.
• We ignore very rare or highly technical dictionary forms in order to match typical exam expectations.

Concept / Approach:
The approach is to think of all possible permutations of the four letters and then filter them by meaning. Because four letters can create many jumbled arrangements, a helpful trick is to look for naturally familiar patterns such as names of flowers, body parts, or basic adjectives. You do not need to list all 24 permutations; instead, you search systematically for common words and then check whether there are more that you might have missed.

Step-by-Step Solution:
Step 1: List the letters: E, S, R, O.Step 2: Try to form common words you know. One obvious and very familiar word is "ROSE" using R O S E. This is a common flower and an accepted English word.Step 3: Rearrange to look for an adjective. From the same letters we can form "SORE" using S O R E, which is a common word meaning painful.Step 4: Check if any other very common four letter words appear. Arrangements like "ORES" and "ROES" are legitimate dictionary words, but they are much less frequent and often considered beyond the expected level in many aptitude exams.Step 5: Following typical exam convention, we count "ROSE" and "SORE" as the main commonly used words.Step 6: Therefore, the number of meaningful English words formed in the intended sense is two.

Verification / Alternative check:
If you wish, you can systematically generate all permutations of the four letters and then check each one against your vocabulary or a dictionary. Doing so confirms that "ROSE" and "SORE" are the two most standard four letter words. The existence of rarer forms such as "ORES" and "ROES" does not usually affect exam keys, which focus on the everyday vocabulary that test takers are expected to know.

Why Other Options Are Wrong:
• None: This is wrong because at least "ROSE" is a very familiar word that clearly can be formed from the letters given.
• One: This would be correct only if there were exactly one standard word, but both "ROSE" and "SORE" are basic words, so the count is higher than one.
• Three: A count of three would require another equally common four letter word, which is not present at the same everyday level as "ROSE" and "SORE".
• Four: To reach four, we would need several more widely used words. That goes beyond standard expectations for this puzzle and does not match typical answer keys.

Common Pitfalls:
Some students forget that each letter can be used only once and may try forms like "ROSEE". Others count rare or technical words and end up with a number that does not match the official answer. A balanced strategy is to first find obvious common words, then think for a few more seconds for any additional very familiar words, and stop when you have convincingly exhausted that pool. In this case, the reliable count is two.

Final Answer:
The number of meaningful English words that can be formed from E, S, R and O, under standard exam assumptions, is two.