In this chapter we consider more closely what we mean by a word. We begin by contrasting the differences between the mental lexicon and dictionaries. We then introduce students to the methods and techniques that psycholinguists use for studying the mental lexicon. We look at reaction time experiments, brain imaging, and the ways in which we can study individuals with aphasia and genetic disorders that affect lexical knowledge. Students are introduced to how children acquire morphology. We then look at English past tense morphology in the context of the ‘storage versus rules’ debate, considering what experimentation, brain imaging, and the study of aphasia and genetic disorders tell us about this controversy. The chapter ends with a brief history of dictionaries.

This chapter begins with the basics of affixation, including the types of morphemes that are commonly found in English (prefixes, suffixes, bound bases, formatives, extenders). Students learn to formulate word formation rules, to represent the internal structure of complex words with tree structures, and to understand difficulties that arise in segmenting words. The chapter also considers the range of meanings that derivational affixes can express. It includes a section on compounding that considers the difficulties in defining what a compound is, the notion of headedness, and the types of compounds that are common in English. The chapter also briefly considers minor types of word formation such as backformation, blending, acronyms, initialisms, and coinage. Students are taught to use corpora such as the Corpus of Contemporary American English to find their own morphological data.

Before we continue our discussion of climate policy, we need to take a detour to examine exponential growth, which may be the most important concept that you have never heard of. It touches many aspects of your life, from the growth of credit card debt and pandemics to governing key processes in biology, physics, economics, and, yes, climate change policy.

This chapter gives brief descriptions of six different contemporary theories of morphology, looking at their philosophical bases, their main concerns and leading questions, and where they stand on the balance between storage versus rules and on the status of the morpheme. The theories we consider are Distributed Morphology (DM), Construction Morphology (CxM), Paradigm Function Morphology (PFM), Natural Morphology (NM), Naïve Discriminative Learning (NDL), and the Lexical Semantic Framework (LSF).

Chapter 11 discussed the options we have to address climate change: adaptation, mitigation, solar radiation management, and carbon dioxide removal. Adaptation will, by necessity, be an important part of our response to climate change. However, relying entirely on adaptation as our only response to climate change is fraught with problems. Geoengineering (solar radiation management and carbon dioxide removal) is another possibility, but one that few people think should be used now. It may help us achieve our climate goals, as we discussed at the end of the last chapter, but no one seriously suggests that it should be our primary way of dealing with climate change.

In the simple model of the climate presented in Chapter 4, the temperature of a planet is set by the number of atmospheric layers (n), the albedo, and the solar constant. I said there that the number of layers is determined by the abundance of greenhouse gases in the atmosphere, but I was intentionally vague about what a greenhouse gas is, or which components of our atmosphere are greenhouse gases. In this chapter, I address these questions and discuss in detail the key greenhouse gas for the problem of modern climate change, carbon dioxide.