This research presents a study on interjections in a functionalist perspective through a comparative analysis on language usages of astonishment and strangeness's expressions in Paulistano and Macanese Portuguese. The theoretical basis and methodological decision are sustained by the Usage-based Linguistics, in a cognitive functional bias, studied in the works of Heine, Claudi and Hünnemeyer (1991), Tomasello (2003), Gonçalves, Lima-Hernandes and Casseb-Galvão (2007), Givón (2009), among other authors. This theoretical field has as its core the concern to deal only with data that preserve the contexts of usage production. Distinguish expressions between astonishment and strangeness is not an easy task in dictionaries or even in grammar books. Currently, it is even impossible to claim for sure that these expressions have a distinction because of the absence of a deeper investigation, focused on pragmatics and mental processes involved jointly with linguistic productions. The general objective of this project is to introduce a new research on interjections, verifying if there are differences in usages of these expressions between the two language varieties investigated and to inquire about the marginalization of this word class by grammarians and linguists. Data utilized for investigation are originated from two materials. The first corpus is composed by audiovisual records derived of Paulistano movies compiled by Guerra (2011) and interviews made by Lima-Hernandes et alii (2012) and Rodrigues (2013). The interjective expressions observed will be compared with a second corpus composed by linguistic usages of Portuguese displayed by Macanese, speakers of Cantonese and Portuguese as mother languages, recorded in theater presentations, informal dialogues and interviews realized by TV and radio programs. Interjections have the pragmatic order as a predominant characteristic because their meanings derive almost exclusively from the intonation of the speaker and the context inserted. Despite of the minimal attention gave by grammarians and linguists, they are communicative strategies heavily utilized in our daily life and, consequently, are a rich source of investigation.