In the following question, four words are given out of which one word is incorrectly spelt. Select the word that is spelt incorrectly.

Introduction / Context:
This spelling question checks whether you can recognise incorrect spellings among common English words. You are given four words, three of which are spelled according to standard dictionary forms and one of which contains a spelling mistake. Your task is to identify the incorrectly spelt word based on your knowledge of correct English orthography.

Given Data / Assumptions:
- Options: Millionaire, Omission, Foreign, Proprietry. - Only one of these is spelled incorrectly. - You must choose the incorrect one, not the correct ones.

Concept / Approach:
The key is to check each word against the standard spelling you have seen in books, articles and dictionaries. Millionaire, omission and foreign are all common words used in everyday writing, and their given forms are correct. The word related to ownership or property is correctly spelled proprietary, with the letters a r y at the end, not r y. The option Proprietry reverses or omits letters in the final syllable and is therefore the misspelt word.

Step-by-Step Solution:
Step 1: Check Millionaire. The correct spelling for someone who has at least one million units of currency is millionaire, with double l and double n. The option matches this spelling. Step 2: Check Omission. Omission is spelled o m i s s i o n, with double s and ending in sion. The option matches this recognised spelling. Step 3: Check Foreign. Foreign is spelled f o r e i g n, with the characteristic e i g n sequence, and the option Foreign is correct. Step 4: Check Proprietry. The related adjective is proprietary, spelled p r o p r i e t a r y. The option uses r y instead of a r y and is therefore incorrect.

Verification / Alternative check:
Think about typical contexts. Proprietary software is a common phrase in computing, and you may also see proprietary medicine or proprietary rights in newspapers and textbooks. In all such uses, the word appears as proprietary, not proprietry. A quick online check in a dictionary or your memory of printed texts should recall this correct pattern. On the other hand, the spellings of millionaire, omission and foreign are very familiar and standard, confirming that they are not the erroneous ones.

Why Other Options Are Wrong (as answers):
Millionaire is not the wrongly spelt word because its double l and double n pattern matches the dictionary form. Omission is not wrong because it correctly uses double s and the sion ending. Foreign is not wrong because it retains the correct sequence e i g n found in many authentic texts.

Common Pitfalls:
Learners sometimes struggle with words that contain e i or i e, or with endings like ary and ery. Exam setters often exploit this by subtly changing the last syllable of a word. To strengthen your spelling, pay special attention to common endings such as ary, ery, ory and patterns like e i g n in foreign and sovereign. Writing these words out a few times or keeping a personal list of frequently tested spellings can greatly improve accuracy in such questions.

Final Answer:
The incorrectly spelt word is Proprietry; the correct spelling is proprietary.