The teaching and learning of science always rely on delivery and communication through language. It is the key factor to affect the success of science learning if the science language is able to generate the science knowledge. However, when talking about the teaching of science, we usually prefer the terminologies to the importance of conjunctions- that connects the terminologies. This study claims that the conjunction plays an indispensable role from the viewpoint of the construction of science knowledge. Without the conjunction, it would become more difficult to generate science explanation and argument. Moreover, the uses of conjunction have effect on learners' to make plausible inferences and their semantic comprehension. Only when being aware of the importance and the necessity of the selection of words and the grammar of describing the relations, the science learners can have the clearer judgments of the logics between different science events and the more complete understanding.