How do I define haploid and monoploid?

[Tyto alba]

I think I understand these terms, not fully though and I can't distinguish between the two and define them.

 

[jim mcnamara]

Monoploid is an old term.

Haploid (1n) implies that alternation of generations exists for an organism. So someday the diploid (2n) "version" will develop. Monoploid is sometimes used for those organisms that seem to have lost the diploid phase. Obviously they cannot ever undergo meiosis. So they reproduce asexually only.

I said "seem to have lost". Why? Example: there are Ascomycetes that literally spend years in the haploid phase, no research has ever found the diploid. Then one day someone finds the "missing generation". Which researchers had known for a long time, too. With the advent of DNA sequencing a lot this kind fog will eventually be lifted.

Stick with the term haploid for (1n) organisms. Nobody will ever fault you for it. Haploid has generally supplanted the use of the term monoploid.