General linguistics encyclopedias

• Encyclopedia of language and linguistics (2nd ed., 2006). A comprehensive 14-volume encyclopedia.
• International encyclopedia of linguistics - Historical, comparative, formal, mathematical, functional linguistics and sociolinguistics
• The Linguistics encyclopedia (2002, 2nd ed) [print]
• Key concepts in language and linguistics
• Concise encyclopedia of languages of the world (2010)
• Encyclopedia of Chinese language and linguistics
• The international encyclopedia of linguistic anthropology (2021)

Research methods

• The Palgrave Handbook of Applied Linguistics Research Methodology
• Research methods in language variation and change
• Research methods in clinical linguistics and phonetics: a practical guide
• Research methods in linguistics (2nd ed, 2018)
• Research methods in sociolinguistics: a practical guide

ESL teaching

• Encyclopedic dictionary of applied linguistics: a handbook for language teaching
• The Routledge encyclopedia of language teaching and learning (2013) (ed. M. Byram)
• Encyclopedia of language and education

Language acquisition

• The Routledge Encyclopedia of Second Language Acquisition

Grammar & usage

• English for Research: Usage, Style, and Grammar (2013)
• Concise encyclopedia of grammatical categories [print]
• The good grammar guide / Richard Palmer, Routledge (2003)
• Cambridge grammar of English: a comprehensive guide: spoken and written English grammar and usage / Cambridge UP, c2006. [print]
• Applying English grammar: functional and corpus approaches / eds. C. Coffin, A. Hewings, K. O'Halloran, c2004) [print]

Phonetics & phonology

• A dictionary of phonetics and phonology / R.L. Trask, 1996
• Understanding phonology / Carlos Gussenhoven and Haike Jacobs
• The atlas of North American English: phonetics, phonology, and sound change / W. Labov et al. [print: Bennett Oversize Books]
• IPA alphabet chart from the International Phonetic Association. A standard for the phonetic representation of all languages.
• Speech Accent Archive - A large number of English speech samples from a variety of language backgrounds and different English speakers.

Semantics

• Concise encyclopedia of semantics [print]
• The Routledge handbook of semantics
• Semantics: an international handbook of natural language meaning / C. Maienborn et al (eds.) [print]

Syntax

• Blackwell Companion to syntax [print]
• Concise encyclopedia of syntactic theories [print]

Sociolinguistics

• A dictionary of sociolinguistics / J. Swann, et al. (2004)
• A glossary of sociolinguistics [print]
• An introduction to sociolinguistics (8th ed. 2021)
• The Routledge companion to sociolinguistics / C. Llamas, et al. [print]
• Data collection in sociolinguistics: methods and applications
• Research methods in sociolinguistics: a practical guide

World languages

• Ethnologue -- A catalogue of the world's languages including information on alternate names, number of speakers, location, dialects, linguistic affiliation, and other sociolinguistic and demographic information. Note: Accessible only with a personal subscription.The Library does not have a subscription for this database, but some information is still freely available on the website. 
• Compendium of the world's languages (2013)
• Atlas of the world's languages / Asher, R.E. and Moseley C., eds. 2nd ed. [print]
• The atlas of languages: the origin and development of languages throughout the world [print]
• The languages of the world / Kenneth Katzner
• The world atlas of language structures/ Martin Haspelmath, ed. [print]
• The Mouton atlas of languages and cultures Vol. 1, Europe and West, Central, and South Asia

Endangered languages

• Atlas of the world's languages in danger [print]
• The Endangered Languages Project - Endangered languages research, revitalization, advocacy, culture, and more.  Information on over 3,300 languages.

Writing systems

• Omniglot - Information about over 200 different writing systems. Each page contains an illustration of a writing system, details of its origin, usage, notable features and the language(s) written with it, as well as a sample text.
• The Routledge Handbook of Scripts and Alphabets