Which suffix means "full of" when added to a base word?

The suffix "ful" means "full of" when it is added to a base word. For instance, in the word "joyful," the base word "joy" combines with the suffix "ful" to indicate that one is full of joy. This usage demonstrates how the suffix modifies the meaning of the base word to convey a sense of abundance or having a certain quality.

In contrast, other suffixes like "less" typically imply a lack of something (e.g., "hopeless" suggests devoid of hope), while "er" often denotes a comparative aspect or something that performs an action (e.g., "teacher" defines someone who teaches). The suffix "ous" conveys a sense of possessing or full of a quality but does not directly align with only meaning "full of" as "ful" does. Hence, "ful" is the most straightforward choice for expressing the idea of being filled with a certain quality or characteristic.