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.

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

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 Access publication of research results
  
• Open Source licensing of software code
  
• Open Dissemination of research data.
  

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.