130. The infinitive may be used as the subject of a verb.
Cf. the complementary infinitive (28), equivalent to the object of a verb, and the use of the infinitive after the prepositions por, anstataŭ, antaŭ ol (98).
Any modifier of the infinitive is necessarily adverbial. An indefinite personal object (or pronominal complement of a preposition) after an infinitive used as subject is expressed by the reflexive pronoun si:
Promeni estas granda plezuro, to go walking is a great pleasure.
Promeni estas agrable, to go walking is pleasant.
Ĉu estas facile rigardi la plafonon? Is it easy to look at the ceiling?
Estas bone sin helpi, it is well to help oneself.
Paroli al si estas malsaĝe, to talk to oneself is silly.
PRESENT ACTION WITH PAST INCEPTION.
131. A present act or state which began in the past is expressed by the present tense (instead of by the past as in English):
Mi estas ĉi tie de lundo, I have been (I am) here since Monday.
De Marto mi studas tiun lingvon, since March I have been (I am) studying that language.
Ili estas amikoj de tiu tago, they have been (they are) friends from that day.
Ni loĝas tie de antaŭ kelkaj monatoj, we have been living (we are living) here since some months ago.
Cf. German er ist schon lange hier, he has already been here a long time, French je suis ici depuis deux ans, I have been here two years, etc.
THE SUFFIX -UL-.
132. The suffix -ul- is used to form nouns indicating a person characterized by or possessing the distinguishing trait, character or quality in the root: