What does it mean to understand science? This commentary extends Brown and Kloser's argument on the role of native language for science learning by exploring the meaning of understanding in school science and discusses the extent that science educators could tolerate adulterated forms of scientific knowledge. Taking the perspective of social semiotics, this commentary looks at the extent that school science can be represented with other discourse practices. It also offers an example to illustrate how everyday language can present potential hindrance to school science learning.