Spirit meant something entirely new to me after my divorce. (Not that divorce is reccomended!)
I grew up hearing "Holy Ghost" or "Holy Spirit" - which used to frighten me, since as a kid I didn't want to have anything to do with a ghost. Yikes.
But having been married once for 8 years, I began to define 'spirit' as something different. It is indeed a life of its own, an existance, so to speak. It is something created. A good friend of mine who is also in the pursuit of holiness, defines spirit as "a bridge". In the example of my former marriage, the "bridge" between my former husband and myself was the emotional and unseen pathway between us. I discovered when we divorced, that the thing that was being rid of, was the spirit of our marriage. Little did I know, this pathway was used so frequently, that it became an entity of itself - a symbol of our togetherness. I believe that when Jesus said, "the two shall become one flesh" this is what he meant. I believe this is also why divorce cannot be put "assunder" since it is what God has made. In my own experience I learned that although the spirit created from marriage can be ignored, it cannot be 'put away'(*see bottom of page). So although this is a depressing example, it did teach me about what a spirit was, and that it is, in fact, a real thing.
So pardon the unfortunate marital example, it only illustrates the point.
The Holy Spirit, then, is the bridge, or relationship between God the Father and God the Son. It is an entity in Itself, because of their relationship. And a strong entity in that Their's is a supremely intense and loyal relationship.
We, by our nature - assuming of course that our nature is both physcial and spiritual - form spiritual relationships all of the time. With our children, our friends - the intensity of the spirit is a result of the stronger bonds. Or if we go a step further into Catholicsm, perhaps the intensity of the spirit is a result of the Vocation. (more on vocations later - but marriage is one of them, religious life, another)
I believe we can form spiritual bonds with inanimate things to a degree - for instance homes can have a "feeling" even if we are just touring an empty house. Rosaries, places of worship or holy objects which serve the purpose of fostering a feeling of holiness to the owner can retain some of the feeling. Walking into a church where genererations have faithfully prayed is an example. In this way, inanimate things take on what we imbue them with - hopefully a happy, hopeful spirit. More like a half-life of a spirit - like the residue from our being there.
The difference is that inanimate objects cannot reciprocate, or "build the bridge" the other way around, as people can, or as God can. To believe so is idolatry in the purest sense.
I believe in order to have a spirtual bond, one must be self aware and have a will.
Now do things (like trees for example) have spirits? I believe all elements have life and are in tune to some degree with their Creator. I do not believe that trees are self-aware. I do not believe they can reciprocate hope, for instance. I do believe they exert life, or a measureable life-force. But this is not the same. You cannot build a spirit bond with inanimate life. This is idolatry because it confuses what the Giver of Life has created. "Made in God's image" implies co-creation and self awareness. It is one of the natures of our existance.
* Regarding Divorce
I believe that through anulment, the spirit of a marriage can be nullified by the spiritual authority granted to the Church by Jesus himself. Although anulments are awarded by the thousands in America alone, they should be approached with the greatest caution. One should not seek an anulment for the freedom to remarry only. And if pursuing an anulment, remember it is the spirit you nulify - you are not merely justifying yourself or cleaning up your past. You are binding a spirit which may be good. So be sure it is not your selfishness which is prevailing. Get good counsel.
Anulments, in my opinion, should be recomended for marriages where one spouse is a murderer, or danger to the family, or where the physical or spiritual "bridge" may cause harm to the family. Such as bad influences which the spouse will not give up in spite of divorce which may actually cause real harm. However, do not confuse a dangerous situation with one that is intended for you to pray your beloved out of. Pray first for your spouse. Needless to say, if you are in physcial danger, get out and pray somewhere safe!