Declaring a sacrament null pertains not only to marriage but to the other sacraments as well. Furthermore, just as the word annulment is inappropriate in regard to marriage, so too would it be inappropriate in regard to other sacraments. The word annulment implies that you are taking "something" and wiping it away. This is not what is being done when a declaration of nullity is granted.
Keep in mind that when a marriage is declared null the Church is really stating, in hindsight, that on the day of the wedding certain factors (consent, its legitimate manifestation, or the legal qualifications of the ministers) prevented the two ministers from bringing about a valid sacrament - as had been presumed!
As legal procedures exist for a marriage case, so too do they exist for declaring the nullity of sacred ordination (cc. 1708-1712). These cases are handled by the appropriate congregation in the Roman Curia or by a tribunal designated by it. Many of the laws governing a tribunal investigation of marriage also apply to this process (cc. 1400-1500; 1501-1670). When a declaration of nullity is granted in regard to sacred ordination, the Church is stating in hindsight that certain factors prevented the bringing about of a valid sacrament of ordination - as had been presumed!
Let's look at another sacrament for a clearer analogy to marriage. Let's take a hypothetical situation in regard to the Eucharist. Unlike marriage, the minister of the Eucharist is "solely a validly ordained priest" (c. 900). On a particular Sunday you go to Church, but the pastor is away. A visiting priest processes to the altar to lead the community in worship. The community prays together, the music is wonderful, the homily is terrific, everyone goes to Holy Communion. Off you go - it was a nice experience.
Two weeks later, it is discovered that the visiting priest wasn't a priest at all. It was a man named John DaSeever who played priest for the weekend! John could be severely punished in church law for his deception, including excommunication (c. 1378). Suppose the deception became public and thereby scandalous. In this case a public declaration of nullity would be warranted.
In hindsight, the Church would publicly declare the Eucharistic consecration null and void. As the Catechism of the Catholic Church states: "Only validly ordained priests can preside at the Eucharist and consecrate the bread and the wine so that they become the Body and Blood of the Lord (CCC, 1411)."
The legal presumption that day had been that bread and wine became the Body and Blood of Christ. Yet in reality that day bread and wine remained bread and wine. When everyone walked up to communion all they received was a piece of bread and a sip of wine. There had been no sacramental effect at the Mass that day. The Eucharist would be declared null. However, it would not be called an annulment of the Eucharist.
Keeping the two sacraments (marriage and Eucharist) in mind, better situates and expresses why the word annulment is inappropriate. At that particular Mass, people gathered together to pray. They were inspired by the music. They may have been moved by the man's talk. They certainly received grace from God. God heard their prayers. They received grace when they approached God with open hearts. All the declaration states is that there was no sacramental effect in regard to the Eucharistic elements at that particular mass. Why? Because something was missing in this "minister" - ordination.
The ministers of marriage are the bride and groom, not the priest. In much the same way, a declaration of nullity in regard to marriage does not deny that one or both of the parties entered the marriage with good intentions. Presumably, they loved one another. They had hopes and dreams. They lived under the operation of God's grace. There were good times and bad times. There were children born of their union.
The declaration does not affect any of that. It simply states that the bond of marriage was not brought about that day. A marriage had not been brought about, as had been presumed. There may have been a defect of consent on the part of one or both ministers. Or, the consent was not legitimately manifested. Or, one or both of the parties may have been incapable according to law to exchange consent. The legal presumption of validity yields to a declaration of nullity.
More often than not, declarations of nullity are granted due to a defect of consent on the part of one or both of the ministers.
Next we will focus on this issue, the consent of the parties ...