There are 3 forms of compound nouns: the closed form (e.g. childlike), the hyphenated form (e.g. son-in-law) and the open form (e.g. post office).
With closed form compounds, it a good idea to check the dictionary for the plural. For a word like 'cupful', the dictionary will give you variant spellings, with the first spelling the preferred, i.e. cupfuls/cupsful.
With hyphenated forms, 's' is usually attached to the element that's being pluralised, so son-in-law becomes sons-in-law. The most significant word takes the plural form. This is also the case with open form compounds, post office becoming post offices.
Change is singular, not plural. The plural form is changes.
To change "puer" (nominative singular) to accusative plural, you need to first change it to the nominative plural form which is "pueri." Then, to get the accusative plural form, change "pueri" to "pueros."
"Stratum" is the singular form of stratum. The plural form is "strata".
The singular form of "lumina" is "lumen."
"Change" can be both singular and plural. It is singular when referring to a single instance of alteration or modification. It is plural when referring to multiple instances of alteration or money in the form of smaller denominations.
Curriculum is singular, curricula is plural.
The compound noun editor-in-chief is the singular form. The plural form is editors-in-chief.
Change is singular, not plural. The plural form is changes.
The plural form of the singular compound noun stepchild is stepchildren.
To change "puer" (nominative singular) to accusative plural, you need to first change it to the nominative plural form which is "pueri." Then, to get the accusative plural form, change "pueri" to "pueros."
The noun 'weekdays' is the plural form. The singular noun is weekday.
The compound noun 'lady in waiting' is the singular form. The plural form is ladies in waiting.
The singular form of the plural compound noun 'mothers-in-law' is mother-in-law.
"Stratum" is the singular form of stratum. The plural form is "strata".
The singular form of "lumina" is "lumen."
"Change" can be both singular and plural. It is singular when referring to a single instance of alteration or modification. It is plural when referring to multiple instances of alteration or money in the form of smaller denominations.
Rife is an adjective. It has no singular or plural form