Hillwalking glossary

How far you must descend from a summit before you can climb to anywhere higher. It measures independence rather than size: a 700 m hill standing alone can have more prominence than a 1,100 m shoulder of a bigger mountain. Nearly every British hill list is defined by a prominence threshold, which is why the same ground yields different lists.

From the data Ben Nevis has the largest drop in our data at 1,345 m — it is an island of high ground in its own right. At the other extreme Carn Dearg Meadhonach stands 1,179 m above sea level but only 27 m above its col, so for all its height it is not counted as an independent hill. Ben Nevis · Carn Dearg Meadhonach

See: The hill lists compared

The lowest point on the highest route between a summit and higher ground — the point you cannot avoid dropping to. Prominence is simply the summit height minus the key col height, so the col is where a hill's classification is really decided.

From the data Ben Macdui reaches 1,309 m and its key col sits at 359 m, giving it 950 m of prominence — the subtraction is the whole of the arithmetic. Ben Macdui

What physically marks the highest point: a cairn, a trig pillar, a boulder, or nothing at all. It matters more than it sounds, because on a broad or flat top the obvious cairn is often not the true summit — surveyors record both, and so do we.

From the data The survey note on Braeriach reads: “top of rock is level with half way up the cairn. Rock 30 E of cairn is just lower. Rock 10 S of cairn at cliff edge is about the same height.” That is why the recorded summit feature is worth reading before you walk to the obvious pile of stones and call it done. Braeriach

A concrete pillar built by Ordnance Survey from 1935 to carry theodolites for the retriangulation of Great Britain. They were sited for sightlines between pillars, not for height, so a trig point is often near a summit rather than on it. Superseded by GPS, and no longer maintained as a network.

The thresholds the classic lists were written around, which is why their metric equivalents look so unround: 3,000 ft is 914.4 m and 2,000 ft is 609.6 m. A resurvey that moves a summit by 30 cm can therefore add or remove a mountain — and has.

See: How the lists are defined

A Scottish mountain of at least 3,000 ft. Uniquely among the major lists there is no prominence rule — whether a 3,000 ft summit is a separate mountain or a subsidiary Top is an editorial judgement, which is why the count has been revised more than once.

See: All 282 Munros

A 3,000 ft Scottish summit that Munro's Tables record as belonging to a mountain rather than being one. Walking the Munros and their Tops is the older, fuller and far less common form of the round.

See: All 226 Munro Tops

Any hill in Britain with at least 150 m of prominence, whatever its height — the purest expression of the independence idea, taking in everything from Ben Nevis to coastal hills of a couple of hundred metres. The name is a joke at the expense of the Munros.

See: Prominence

Two further prominence lists: a HuMP is a hill with at least 100 m of drop, a Simm a summit of at least 600 m with at least 30 m of drop. Both run to thousands of hills, which is why OpenFell carries only the part of each that qualifies on another list too.

See: Exactly how far our coverage goes

One of the 214 Lake District fells given a chapter in A. Wainwright's Pictorial Guides. There is no rule behind it — he chose them — so unlike every measured list this one cannot change with a resurvey.

See: All 214 Wainwrights

A 3,000 ft summit outside Scotland. "Furth" is Scots for beyond: these are the hills that would be Munros were they north of the border.

See: The Furths

The highest point of a county. OpenFell uses the historic pre-1974 counties because they are stable — modern council areas have been redrawn repeatedly, and each redrawing invents and abolishes summits, some of them roundabouts and retail parks.

See: The historic county tops

Working through a list. What counts as bagged is entirely a matter of personal rule — summit reached on foot, in a single day, from the valley, in winter — and no authority adjudicates it.

See: Track a round

The set of summits belonging to one independent hill, in the sense above. It is a statement about drop, not about ridgelines: over a big massif a group can gather hills nobody would walk together, and which few would call parts of the same mountain.

Mapped mountain, moor, heath, down and registered common in England and Wales where the Countryside and Rights of Way Act 2000 gives a right of access on foot. Shown yellow-shaded on OS Explorer maps. It is a right to walk, not to camp, cycle or drive.

See: Access rights in England · in Wales

Scotland's statutory right, under the Land Reform (Scotland) Act 2003, to go on most land and inland water for recreation — not confined to paths and not confined to open country. Exercised under the Scottish Outdoor Access Code.

See: Access rights in Scotland

A highway the public may use regardless of who owns the land beneath it, recorded on a definitive map held by the highway authority. The right follows the line of the path; it does not extend to the field either side.

See: Definitive map

The legal record of public rights of way in England and Wales. Its authority is conclusive as to what it shows, but it is not exhaustive — the Ramblers identified some 49,000 miles of historic paths missing from it, and the deadline for registering them is currently unresolved.

See: The 2031 deadline question

A route in a Scottish access authority's core paths plan, intended to give reasonable access across its area. In Scotland these supplement the general access right rather than defining its limits — you are not confined to them.

See: Access rights in Scotland

A route open by the landowner's consent rather than by right. It can be closed or rerouted at any time, and use of it does not accrue into a public right of way. Most countryside access in Northern Ireland works this way.

See: Access rights in Northern Ireland

Being on land without permission or right. In England, Wales and Northern Ireland it is generally a civil matter, not a crime — the landowner may ask you to leave and sue for any damage, but no offence is committed by the act of being there. Aggravated trespass, and trespass on railways and military land, are separate and are criminal.

Camping away from a site, lightweight and for a night or two. Lawful as part of the access right in Scotland, and on the Dartmoor commons following the Supreme Court in 2025. Everywhere else in England, Wales and Northern Ireland it needs the landowner's permission.

See: Wild camping, nation by nation

A local rule made by a park authority, council or other body, which can restrict what the general law otherwise permits. The camping-management zones in Loch Lomond & The Trossachs are the clearest example: the national access right applies, and the byelaws still require a permit.

Under the CRoW Act a landowner may close or restrict open access land for up to 28 days a year without giving a reason, with longer restrictions available for land management and fire risk. Check before travelling — a closure is lawful whether or not there is a sign at the gate.

A position on the Ordnance Survey National Grid, given as two letters and an even number of digits. Each pair of extra digits multiplies the precision tenfold: six figures locates you to 100 m, eight to 10 m, ten to 1 m. Peak pages carry ten figures where DoBIH records them.

See: Convert a grid reference

Two different models of the Earth's shape. OS grid references are built on OSGB36; GPS and web maps use WGS84. The same point has different coordinates in each, and the gap across Britain runs to roughly 70–120 m — enough to put you on the wrong side of a crag.

See: Convert between them

The two OS paper series. Landranger is 1:50,000, pink covers, good for planning a day across a wide area. Explorer is 1:25,000, orange covers, and shows field boundaries and access-land shading — the one to carry on the hill.

The classic time estimate: an hour for every 5 km, plus an hour for every 600 m of ascent. It describes a fit walker on good ground with a light pack and no stops, so it is best read as a floor. Langmuir's corrections adjust it for descent and rough ground.

See: Walking-time calculator

The standard interchange format for routes and tracks — plain XML, readable by every GPS unit and mapping app. A track records where you actually went; a route records where you intend to go.

See: Analyse a GPX file

The period after sunset while the sun is less than 6° below the horizon, during which you can still usefully see without a torch. It is the honest end of your day's light, and on a UK hill in December it can close within half an hour of sunset.

See: Daylight safety planner

A bowl gouged into a mountainside by a glacier, usually steep-walled on three sides and often holding a lochan or tarn. Coire in Gaelic, cwm in Welsh — both appear constantly in hill names.

The low point on a ridge between two summits — the natural crossing place, and usually the key col that decides a hill's prominence.

See: Key col

A narrow rock ridge, formed where two corries have eaten into a mountain from either side. Striding Edge on Helvellyn and the Aonach Eagach are the best-known British examples; several are scrambles rather than walks.

A simple unlocked shelter in remote country, usually a former cottage, with no beds, no facilities and no booking. Most are maintained by volunteers on the owner's goodwill, under a code that asks for small parties, short stays and leaving it better than you found it.

A hill or mountain in northern England, from Old Norse fjall. Related local words are equally specific: a pike is a peaked summit, a how a rounded one, a knott a rocky one, and a tarn a small mountain lake.

An exposed outcrop of weathered rock standing above the surrounding ground, characteristic of Dartmoor and the granite moors of the south-west. Many are the recorded summit feature of their hill.

Gaelic: beinn or ben (mountain), meall (rounded hill), sgurr (rocky peak), stob (point), carn (cairn or heap), creag (crag), dubh (black), dearg (red), mor (big), beag (small). Welsh: y wyddfa (the tumulus), moel (bare hill), carnedd (cairn), glyder (heap), llyn (lake), bwlch (pass), mynydd (mountain).

From the data Around 628 of the 1,740 hills on OpenFell carry a Gaelic name or name element, so this vocabulary covers a good deal of the Scottish map on its own.