English as a lingua franca (ELF) is the use of the English language "as a common means of communication for speakers of different first languages”.[1] ELF is also “defined functionally by its use in intercultural communication rather than formally by its reference to native-speaker norms”[2] whereas English as a foreign language aims at meeting native speaker norms and gives prominence to native speaker cultural aspects.[3] While lingua francas have been used for centuries, what makes ELF a novel phenomenon is the extent to which it is used – both functionally and geographically. A typical ELF conversation may involve an Italian and a Dane chatting at a coffee break of an international conference held in Brussels, a Spanish tourist asking a local for the way in Berlin, and many other similar situations.

The way English is used as a lingua franca is heavily dependent on the specific situation of use. Generally speaking, ELF interactions concentrate on function rather than form. In other words, communicative efficiency (i.e. getting the message across) is more important than correctness.[4] As a consequence, ELF interactions are very often hybrid.[5] Speakers accommodate to each other's cultural backgrounds and may also use code-switching into other languages that they know.[6] Based on the Vienna-Oxford International Corpus of English (VOICE) and additional research, the following features of ELF lexicogrammar have been identified:[7][8]

However, these features are by no means invariant or “obligatory”. Rather, these forms do not seem to compromise effective communication within an ELF setting when they do occur.

English as a lingua franca (ELF) can be defined as “an additionally acquired language system which serves as a common means of communication for speakers of different first languages”. Here's the Wikipedia entry for ELF.

Via Nicos Sifakis