Below is a list of definitions to help those unfamiliar with the terms understand the data and concepts explored on the site.

Ribu – A mountain with a topographic prominence of 100 metres or more. Also known as P1000 where P stands for prominence. The word ‘ribu’ means thousand in Indonesian and Malay.

Height – Also known as elevation. This is the height above sea level of a mountain summit. For example, the height of Ben Nevis is 1345m above sea level.

Prominence / topographic prominence – The height of a mountain or hill’s summit relative to the lowest contour line encircling it but containing no higher summit within it. It is a measure of the independence of a summit. Also known as drop and relative height. In the listings, every mountain has a prominence such as P1892. In this example the mountain has a drop/relative height/prominence of 1892 metres. The highest peak of any island will have the same identical height and prominence figures includind Ben Nevis above which is 1345m above sea level and also P1345, due to the key col being sea level.

Key col – The lowest point on the highest connecting ridge connecting to a higher peak. Also known as key saddle. In the case of Ben Nevis, above, the key col is 0 (zero) at sea level. Topographic prominence / drop / relative height is calculated by subtracting the key col figure from the elevation or height figure. For example, Gunung Dempo in Sumatra, Indonesia is 3173m high and has a key col at 723m. 3173 minus 723 gives a figure of 2450 which means Gunung Dempo has a prominence of 2450 metres (P2450).

Name – Some famous mountains have several names in multiple languages. To keep things simple, we have included a maximum of 2 names for each mountain entry. We have aimed to retain the 2 most relevant names though this is not always an easy task. Derived names are noted with an asterisk and typically taken from the nearest river, lake, other landmark or settlement found on maps that have not already given their names to another nearby peak.

Location – Decimal degrees for summit co-ordinates using latitude and longitude are provided for each mountain entry.

Country – We use the public domain Natural Earth dataset to determine which country each peak is located in. Many are on international borders and some regions/territories are disputed. We use the Mountain Range Classification System (PEMRACS) to divide the list into regions for display on the site.

ID – Each mountain in the list has a unique identification number.

Ultra – Short for ‘ultra-prominent peak’. There are approximately 1524 of these peaks which need a minimum of 1500 metres of prominence to qualify for inclusion in the list. In other words, P1500s.

Bagger – A person who seeks to collect something, mountain peaks in the case of peakbaggers. Peakbaggers tend to collect things on a published list, such as the Ultras (P1500), Ribus (P1000), Marilyns (P150), and so on.