* Definition of "second" is unclear: Do we mean the language spoken by the second-largest number of native speakers? Or the second most common language overall, including non-native speakers?
* Data is complex: The number of speakers can vary significantly depending on the source and how "speaker" is defined (native vs. non-native, fluent vs. conversational).
* Language families: Many languages are closely related, making it tricky to separate them. For example, should we count all varieties of Chinese as one language, or separate them?
Common contenders for the "second language" title include:
* Hindi: Often listed as having the largest number of native speakers after Mandarin Chinese.
* English: While not having as many native speakers as Hindi, English has far more non-native speakers, making it the most widely spoken language in the world.
* Spanish: Spanish has a large number of native speakers and is growing rapidly in several parts of the world.
* Arabic: Arabic is spoken by a large number of people across the Middle East and North Africa.
Therefore, it's not possible to definitively say which language is "second." The answer depends on how you define "second" and what data sources you use.