How to use the Korean particle picker
English has no rule quite like this one. In Korean, the small grammatical particle that follows a noun changes shape depending on whether the noun ends in a final consonant, called batchim. Paste a list of words, one per line, and this tool picks the right form of the most common particles for each of them.
The decision comes from the Unicode formula rather than a word list. Subtract the start of the precomposed Hangul block from the last syllable and take the remainder modulo 28; that number is the final consonant, and zero means there is none. A word with a final takes i, eul, eun, gwa, irang and a, while a word without one takes ga, reul, neun, wa, rang and ya.
The (eu)ro particle follows a different rule. It becomes ro not only after a vowel but also after the consonant rieul, so a word ending in rieul behaves like a vowel-final word here while every other final takes euro. The table flags rieul finals separately so the reason is visible at a glance.
Words ending in digits are handled too, based on how the number is read aloud in Korean: 1 is read il and ends in rieul, while 10 is read sip and ends in a different consonant. Numbers ending in zeros are read by their place value, up to the Korean unit for a trillion, and a decimal is judged by its last fractional digit. Words ending in Latin letters are deliberately not supported, because Korean readings of the alphabet vary from speaker to speaker; those rows are marked as unresolved and counted above the table.
Frequently asked questions
That particle treats rieul as an exception. Words with no final and words ending in rieul both take ro, while every other final consonant takes euro.
By the last sound of the Korean reading. 1 is read il and ends in rieul, 10 is read sip and ends in a consonant, and 2 is read i with no final at all.
How an alphabet letter is read in Korean depends on the speaker and the context, so no single answer holds. Rather than guess wrong, the tool says it cannot tell.