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18.2.3 exercise: the gerundio as an adverb and as an adjectiv
As the present participle in English, in opposite to the English gerund, the Portuguese gerundio can be adverb and adjective.
the present participle as an adjective (only possible with intrasitive verbs, in case of a transitive verb a direct object is needed)
The rattling machines made an awful noise.
Barking dogs don't bite.
The crying crowed moved forward to the train station.
The English gerund is a verbal noun and only something that can have the function of noun can be used after a preposition. The English gerund is normally translated with an infinitive to Portuguese.
English gerund Portuguese infinitive
Without knowing what to do, I went home earlier.
Sem saber o que fazer, fui para casa mais cedo.
Before opening the letter, she took a deep breath.
Antes de abrir a carta, ela respirou fundo.
From a purely logical perspective, something completely irrelevant if we talk about linguistic issues, the gerundio can't be used as an adjective. An adjective agrees in gender and number with the noun it refers to. (At least in any other language. English is in exception: the red flower => the red flowers. The adjective red doesn't change. In other languages it would be "the reds flowers" or something like that.) Therefore the use of the gerundio as an adjective is questioned in roman languages, most of all in Spanish. In French and Italian it is more or less accepted, see Present participle as adjective, while in Spanish its use as an adjective is bluntly rejected.
El uso del gerundio acompañando a un sustantivo y complementando su significado es incorrecto para la RAE, excepto en dos casos concretos: «agua hirviendo» y «clavo ardiendo».
The use of the gerundio as an attribut to a noun in order to precise the meaning is not correct following the Real Academia Española. There are only two exceptions: "Agua hirviendo", boiling water and "clavo aradiendo", final straw.
In Portuguese the attributive use, as an adjective, is often mentioned, but rarely described in detail. However the empirical facts are clear. With expressions like "uma criança sorrindo" (a lauging child), "pessoas falando" (speaking people), "meninos brincando" (playing children), "mulheres lendo" (reading women) we get thousands of results if we put them in a search engine. (Don't forget to use quotation marks, otherweise you will get all the pages where the twoe words show up in any order. If we compare the Portuguese results with the corresponding Spanish expressions "personas hablando", "niños jugando", the picture is quite similar and we can therefore deduce that a lot of people don't care what the Real Academia Española says.
* There is no generic word for children in Spanish. Therefore we have to add both sexes. Then we get 324 000 results.
Put the gerundio in the following sentences and decide whether it is used as an adjective or an adverb. Used as an adverb or an adjective it doesn't describe a causal, temporal, modal, conditional or concessive relationship between the action described by the finite verb and the action described by the infinite verb. It doesn't stand for a subordinate clause. Used as an adverb it refers to a verb and describes the way the action / event described by this verb is performed. Used as an adjective, it assigns a characteristic to the noun.