This piece could just as easily add on the the attached Greeting and Polite Speech article, but instead it will be its own topic with a link to the larger overall topic. We will be considering how Common handles the concept of welcome - the short answer is that more or less calques the English idea of 'well come', but there are certain subtleties that need to be considered.
Welcome as Set Greeting: Zra Falu!
The set phrase 'zra falu' is the most frequent expression for 'welcome' that you will see. For example, it is what you would see written on a sign welcoming you to a town. It is a defective statement (see attached article), generally interpreted as a verb which is which is missing its auxiliary, in which case it has a sense like 'well come'. We can see this in the fact that if there is a 'to X' part added, as in 'Welcome to St. John's', the 'to' part is put in the dative case, as in 'Zra Falu ija Syncán'.
Be Welcome: Noxot Zra Falu/Se An Ewisys
To convey the idea that one is welcome at a place, the proper statement form 'noxot zra falu' (the perfect aspect is typically used) can be used. For example, the sentence 'zu sy noxot zra falu ija spet costo' means 'you are welcome in this house'.
You can also use the modifier 'ewisys', invited or welcome, to convey the same idea. 'Zu sy se an ewisys e na spet costo' is a way of saying the same thing, 'you are welcome in this house'.
The Act of Welcoming: Te Hisy/Te Ewis
To talk about someone being welcomed, the verbs 'te hisy' or 'te ewis' would be employed. 'Hisy' means literally 'honour' and is also one of the main words to talk about greeting. 'Ewis' means 'invite' or 'summon'. There is a different shade of meaning between these two words when talking about welcoming someone - hisy is used more to talk about the immediate act of greeting, and ewis about inviting someone in. As well, 'hisy' can have sense other than welcoming someone in, although its connotations are always positive, whereas 'ewis' may focus less on the act of greeting but is always about inviting someone in.
There is also a combined form 'te hisy e na ewis', as in 'jer zu sy te hisy e na ewis', which translates approximately to 'we (exclusive) honour you sir in invitation' and unambiguously combines the senses of both terms.
These words can be used somewhat interchangeably in many situations, but the choice of words will sometimes matter for your Common to sound idiomatic and polished.