The Portuguese word meio can mean a precise measurement ("half") or a vague state of being ("kind of" or "somewhat"). Telling them apart comes down to whether the word changes to match gender and number.
"Half": The Variable Adjective
When meio means "half", it acts as an adjective and must agree in gender and number with the noun it describes (like changing to meia for feminine nouns).
| She ate half an apple pie. | Ela comeu meia tarte de maçã. |
| What a pity! She drank only half a goblet of wine. | Que pena! Ela bebeu apenas meia taça de vinho. |
"Kind of": The Invariable Adverb
When meio means "kind of" or "somewhat", it acts as an adverb. Adverbs are invariable, meaning meio never changes its form—even if it applies to a feminine or plural subject. (The adjective describing the actual feeling, however, does still change to match the subject!)
| The girl stood up very fast and got kind of dizzy. | A rapariga levantou-se muito rápido e ficou meio tonta. |
| The doctor is no longer kind of depressed thanks to you. | A médica já não está meio deprimida graças a ti. |
Notice how the state adjectives (tonta and deprimida) change to match the feminine subjects, but the adverb meio stays exactly the same.
Spotting the Difference
It is common to mix both uses of meio in the same sentence. In the examples below, the word for "half" changes to match the noun it measures, but the word for "kind of" stays frozen as meio—even as the emotional states (enjoada, surpreendidos, desiludidos) agree with the subjects.
| The doctor is kind of nauseous after eating half a pie. | A médica está meio enjoada depois de comer meia tarte. |
| They were kind of surprised when they saw half a pie on the table. | Eles ficaram meio surpreendidos quando viram meia tarte na mesa. |
| They watched half a movie and got kind of disappointed. | Eles viram meio filme e ficaram meio desiludidos. |