One of the factors that can influence how you learn another language would be your native language or the existing language that you already speak and know. Languages that share similar qualities with your native tongue will be easier to learn, while others that have little or nothing in common will be difficult to handle. Other languages may fall in the middle.

Languages related to your native language or languages that you speak are also easier to learn and grasp because there are less new concepts to study. For example if your language is English, a Germanic language, its related languages German, Dutch, Swedish, Norwegian and Danish would be easier to learn. Languages like Chinese and Korean that share no ancestry with the English language would be difficult to learn.

Similar grammar rules may be shared by related languages but not in all instances. For example, German and English are related languages but grammar of the German language is relatively complex. While Chinese and English are totally unrelated languages they share similarities when it comes to grammar.

Borrowed words and vocabulary can make learning a language easier. It is important to note that many words in English have Latin origins and you can as well find many French words borrowed by the English language.

The different language sounds can make language learning tricky. You will discover that a certain language may have sounds that didn't even exist in your native tongue and are very hard to articulate and pronounce.

Some languages use tones and are effectively learned when you hear them from native speakers.

The language's writing system varies while you may find many using similar English scripts with a few added symbols specific to a particular language. Other languages though actually have a totally different alphabet with some languages having the writing starting from the right instead of the usual which is on the left. Asian languages like Korean, Japanese and Chinese have a totally different writing system with Chinese proving to be the greatest challenge to learn.

Certain languages incorporate part of their culture into the language. While in your native language for example you can just speak politely, in certain languages like those in Europe how you address a person or who you are talking to would be affected by the choice of words that you should be using for example for the word "you"

Other than your native tongue and other languages that you know how to speak of, other factors like your intelligence, memory, talent for languages and listening ability are other factors that could affect your ability to learn a new language.