Formations are described by how the players are categorized in accordance to their positioning along; and not across, the pitch, with the more defensive-oriented players listed first. For example, the formation 4–3–3 means four defenders, three midfielders and three forwards.
Typically, goalkeepers are not included in these types of descriptions. However when they are, they are simply listed first, such as 1-4-3-3, using the example above.
Traditionally, those within the same category; the 4 midfielders in a 4–4–2, for example, would generally play as a fairly flat line across the pitch with those players in the wide positions often playing in a slightly more advanced role. However, in many modern formations this is no longer the case, which has led to modern formation interpretations splitting certain formations down into in two separate categories, some even being broken down even further into four or even five additional numbered formations. A common example is the 4–2–1–3, where the midfielders are split into two defensive and one offensive player. This formation is also considered a kind of
4–3–3.
It was not until the 4-2-4 system was developed and then implemented in the 1950s that the numbering system was put into place.