Glossary of Terms

All complex subjects have their own terminology that sometimes makes it hard for new people to break into the field. This sometimes includes uncommon words, but more often than not a subject will have very specific meanings for common words - the discussion of errors vs mistakes in this video is a good example of this.

This glossary is a reference of some of the uncommon terms and specific definitions of more common words that you will encounter throughout Data Tree and your broader dealings with data. 

Many of these definitions come from the course materials and experts that helped develop Data Tree. Others come from the CASRAI Dictionary. Those definitions are kindly made available under a Creative Commons Attribution 4.0 International License.

Browse the glossary using this index

Special | A | B | C | D | E | F | G | H | I | J | K | L | M | N | O | P | Q | R | S | T | U | V | W | X | Y | Z | ALL


Observational research data

Research data captured in real time, usually unique and irreplaceable. 

Examples: Weather records, species census surveys.


A set of terminology to describe important concepts, often specific to a particular domain or discipline. It's a way of describing a vocabulary that can be shared among practitioners in a field, to allow for easier communication and a standardised way of defining and labelling, for example when writing metadata.

Open Data

Structured data that are accessible, machine-readable, usable, intelligible, and freely shared. Open data can be freely used, re-used, built on, and redistributed by anyone - subject only, at most, to the requirement to attribute and share-alike.

-  CASRAI Dictionary

Open Science

The practice of science in such a way that others can collaborate and contribute, where research data, lab notes and other research processes are freely available, under terms that enable reuse, redistribution and reproduction of the research and its underlying data and methods. 

- FOSTER Open Science Consortium

Open Science encompasses a broad set of practices, including: 

Open Source

Open source software is software whose source code has been made freely available for re-use and modification under and Open Source license. 

There are different types of open source license, but to be truly open source they all conform to the guidelines laid out at the Open Source Initiative

Ordinal variable

An ordinal variable is a categorical variable in which the categories have an obvious order, e.g. (strongly disagree, disagree, neutral, agree, strongly agree), or (dry, trace, light rain, heavy rain).


A data point showing an unexpected relationship or large difference to the remainder of the dataset.